Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced by Knowmade with collaboration from the managers of GANEX groups. The newsletter presents a selection of newest scientific publications, patent applications and press releases related to III-Nitride semiconductor materials (GaN, AlN, InN and alloys)

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Cluster of Excellence (Labex, 2012-2019) GANEX is a cluster gathering French research teams involved in GaN technology. The objective of GANEX is to strengthen the position of French academic players in terms of knowledge and visibility, and reinforce the French industrials in terms of know-how and market share. www.ganex.fr

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GANEX Newsletter No. 37 February 2016

III-N Technology

KnowMade

GANEX | Newsletter No. 37 - III-N Technology 2

METHODOLOGY

Each month

250+ new scientific publications

120+ new patent applications

20+ new press releases

Sources 10+ scientific journal editors

Elsevier, IOP, IEEE, Wiley, Springer, APS, AIP, AVS, ECS, Nature, Science …

10+ specialist magazines Semiconductor Today, ElectoIQ, i-micronews,

Compound Semiconductor, Solid State Technology … 5+ open access database: FreeFulPDF, DOAJ …

Patent database: Questel-Orbit

Selection by III-N French

experts

GANEX monthly newsletter

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GANEX | Newsletter No. 37 - III-N Technology 3

TABLE OF CONTENTS (clickable links to chapters)

SCIENTIFIC PUBLICATION ................................................................................................................... 4

GROUP 1 - LEDs and Lighting ................................................................................................................... 4

GROUP 2 - Laser and Coherent Light ....................................................................................................... 8

GROUP 3 - Power Electronics ................................................................................................................. 11

GROUP 4 - Advanced Electronics and RF ............................................................................................... 17

GROUP 5 – MEMS and Sensors .............................................................................................................. 22

GROUP 6 - Photovoltaics and Energy harvesting ................................................................................... 24

GROUP 7 - Materials, Technology and Fundamental............................................................................. 26

PRESS RELEASE ................................................................................................................................ 42

PATENT APPLICATION ...................................................................................................................... 49

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GANEX | Newsletter No. 37 - III-N Technology 4

SCIENTIFIC PUBLICATION Selection of new scientific articles

GROUP 1 - LEDs and Lighting Group leader: Benjamin Damilano (CRHEA-CNRS)

Information selected by Benjamin Damilano (CRHEA-CNRS)

Hybrid tunnel junction contacts to III–nitride light-emitting diodes Materials Department, University of California, Santa Barbara, CA 93106, U.S.A. Applied Physics Express http://dx.doi.org/10.7567/APEX.9.022102

In this work, we demonstrate highly doped GaN p–n tunnel junction (TJ) contacts on III–nitride heterostructures where the active region of the device and the top p-GaN layers were grown by metal organic chemical vapor deposition and highly doped n-GaN was grown by NH3 molecular beam epitaxy to form the TJ. The regrowth interface in these hybrid devices was found to have a high concentration of oxygen, which likely enhanced tunneling through the diode. For optimized regrowth, the best tunnel junction device had a total differential resistivity of 1.5 × 10−4 Ω cm2, including contact resistance. As a demonstration, a blue-light-emitting diode on a ($20\bar{2}\bar{1}$) GaN substrate with a hybrid tunnel junction and an n-GaN current spreading layer was fabricated and compared with a reference sample with a transparent conducting oxide (TCO) layer. The tunnel junction LED showed a lower forward operating voltage and a higher efficiency at a low current density than the TCO LED. Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions Graduate Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University (NTU), No.1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan R.O.C Scientific Reports http://dx.doi.org/10.1038/srep19757

The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC1−x) buffer is demonstrated. The a-

SixC1−x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC1−x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC1−x buffer. The C-rich SixC1−x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC1−x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich SixC1−x buffer, the device deposited on C-rich SixC1−x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively. Efficiency Drop in Green InGaN/GaN Light Emitting Diodes: The Role of Random Alloy Fluctuations Department of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico 1, 00133 Rome, Italy Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.116.027401

White light emitting diodes (LEDs) based on III-nitride InGaN/GaN quantum wells currently offer the highest overall efficiency for solid state lighting applications. Although current phosphor-converted white LEDs have high electricity-to-light conversion efficiencies, it has been recently pointed out that the full potential of solid state lighting could be exploited only by color mixing approaches without employing phosphor-based

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wavelength conversion. Such an approach requires direct emitting LEDs of different colors, including, in particular, the green-yellow range of the visible spectrum. This range, however, suffers from a systematic drop in efficiency, known as the “green gap,” whose physical origin has not been understood completely so far. In this work, we show by atomistic simulations that a consistent part of the green gap in c-plane InGaN/GaN-based light emitting diodes may be attributed to a decrease in the radiative recombination coefficient with increasing indium content due to random fluctuations of the indium concentration naturally present in any InGaN alloy. Facile Formation of High-Quality InGaN/GaN Quantum-Disks-in-Nanowires on Bulk-Metal Substrates for High-Power Light-Emitters Photonics Laboratory, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia Nano Lett. http://dx.doi.org/10.1021/acs.nanolett.5b04190

High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light-emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrates. The LEDs exhibited a low turn-on voltage of ∼2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ∼5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector, and heat sink, which greatly simplifies the fabrication process of high-power light-emitters. Our work

ushers in a practical platform for high-power nanowires light-emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates. Green Emitting Cubic GaInN/GaN Quantum Well Stripes on Micropatterned Si(001) and Their Strain Analysis Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA Advanced Electronic Materials http://dx.doi.org/10.1002/aelm.201500327

GaInN/GaN heterostructures in the cubic lattice variant have the potential to overcome the limitations of wurtzite structures as commonly used for light emitting and laser diodes. Wurtzite GaInN (0001), suffers from large internal polarization fields, which force design compromises toward ultranarrow quantum wells and reduce recombination volume and efficiency, particularly in the green, yellow, and red visible spectral regions. Cubic GaInN microstripes on micropatterned Si(001), with {111} V-grooves oriented along Si inline image, offer a system free of internal polarization fields, wider quantum wells, and a smaller bandgap energy. 6 and 9 nm Ga1-xInxN/GaN single quantum well structures are prepared and their emission spectra found to be dominated by the recombination in the cubic wells. The peak wavelength ranges from 520 to 570 nm with a polarization predominately perpendicular to the grooves. These values are about 26 nm longer in wavelength than the equivalent wurtzite inline image sample portions and 40 nm longer than the wurtzite (0001) oriented portions. An alloy composition range of 0.2 < x < 0.3 has been estimated in those cubic portions and quantum efficiency comparable to planar wurtzite structures. The stripe geometry and photon polarization may be suitable for optical mode confinement and reduced threshold stimulated emission.

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GANEX | Newsletter No. 37 - III-N Technology 6

Variation of the external quantum efficiency with temperature and current density in red, blue, and deep ultraviolet light-emitting diodes Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, South Korea J. Appl. Phys. http://dx.doi.org/10.1063/1.4939504

The temperature-dependent external quantum efficiencies (EQEs) were investigated for a 620 nm AlGaInP red light-emitting diodes(LEDs), a 450 nm GaInN blue LED, and a 285 nm AlGaN deep-ultraviolet (DUV) LED. We observed distinct differences in the variation of the EQE with temperature and current density for the three types of LEDs. Whereas the EQE of the AlGaInP red LED increases as temperature decreases below room temperature, the EQEs of GaInN blue and AlGaN DUV LEDs decrease for the same change in temperature in a low-current density regime. The free carrier concentration, as determined from the dopantionization energy, shows a strong material-system-specific dependence, leading to different degrees of asymmetry in carrier concentration for the three types of LEDs. We attribute the EQE variation of the red, blue, and DUV LEDs to the different degrees of asymmetry in carrier concentration, which can be exacerbated at cryogenictemperatures. As for the EQE variation with temperature in a high-current density regime, the efficiency droop for the AlGaInP red and GaInN blue LEDs becomes more apparent as temperature decreases, due to the deterioration of the asymmetry in carrier concentration. However, the EQE of the AlGaN DUV LED initially decreases, then reaches an EQE minimum point, and then increases again due to the field-ionization of acceptors by the Poole-Frenkel effect. The results elucidate that carrier transport phenomena allow for the understanding of the droop phenomenon across different material systems, temperatures, and current densities.

White-light emission from InGaN/GaN quantum well microrings grown by selective area epitaxy School of Science, Jiangsu Provincial Research Center of Light Industrial Optoelectronic Engineering and Technology, Jiangnan University, Wuxi 214122, China School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China Photonics Research http://dx.doi.org/10.1364/PRJ.4.000017

Monolithic white-light-emitting diodes (white LEDs) without phosphors are demonstrated using InGaN/GaN multiple quantum wells (MQWs) grown on GaN microrings formed by selective area epitaxy on SiO2 mask patterns. The microring structure is composed of {1-101} semi-polar facets and a (0001) c-plane, attributed to favorable surface polarity and surface energy. The white light is realized by combining short and long wavelengths of electroluminescence emissions from InGaN/GaN MQWs on the {1-101} semi-polar facets and the (0001) c-plane, respectively. The change in the emission wavelengths from each microfacet is due to the In composition variations of the MQWs. These results suggest that white emission can possibly be obtained without using phosphors by combining emission light from microstructures. Fabrication, characterization and applications of flexible vertical InGaN micro-light emitting diode arrays Institute for Electric Light Sources, Fudan University, Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai, China Institute of Photonics, Department of Physics, University of Strathclyde, Glasgow, UK Optics Express http://dx.doi.org/10.1364/OE.24.000699

Flexible vertical InGaN micro-light emitting diode (micro-LED) arrays have been fabricated and characterized for potential applications in flexible micro-displays and visible light communication. The LED epitaxial layers were transferred from initial sapphire substrates to flexible AuSn substrates by metal bonding and laser lift off techniques. The current versus voltage characteristics of flexible micro-LEDs degraded

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after bending the devices, but the electroluminescence spectra show little shift even under a very small bending radius 3 mm. The high thermal conductivity of flexible metal substrates enables high thermal saturation current density and high light output power of the flexible micro-LEDs, benefiting the potential applications in flexible high-brightness micro-displays and high-speed visible light communication. We have achieved ~40 MHz modulation bandwidth and 120 Mbit/s data transmission speed for a typical flexible micro-LED. A physical model for the reverse leakage current in (In,Ga)N/GaN light-emitting diodes based on nanowires Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, D-10117 Berlin, Germany J. Appl. Phys. http://dx.doi.org/10.1063/1.4940949

We investigated the origin of the high reverse leakage current in light emitting diodes(LEDs) based on (In,Ga)N/GaN nanowire (NW) ensembles grown by molecular beam epitaxy on Si substrates. To this end, capacitance deep level transient spectroscopy(DLTS) and temperature-dependent current-voltage (I-V) measurements were performed on a fully processed NW-LED. The DLTSmeasurements reveal the presence of two distinct electron traps with high concentrations in the depletion region of the p-i-n junction. These band gap states are located at energies of 570 ± 20 and 840 ± 30 meV below the conduction band minimum. The physical origin of these deep level states is discussed. The temperature-dependent I-V characteristics, acquired between 83 and 403 K, show that different conduction mechanisms cause the observed leakage current. On the basis of all these results, we developed a quantitative physical model for chargetransport in the reverse bias regime. By taking into account the mutual interaction of variable range hopping and electron emission from Coulombic trap states, with the latter being described by phonon-assisted tunnelling and the Poole-Frenkel effect, we can model the experimental I-V curves in the entire range of temperatures with a consistent set of parameters. Our model should be applicable to

planar GaN-based LEDs as well. Furthermore, possible approaches to decrease the leakage current in NW-LEDs are proposed. Study on efficiency droop in InGaN/GaN light-emitting diodes based on differential carrier lifetime analysis Tsinghua National Laboratory for Information Science and Technology, Department of Electronic Engineering, Tsinghua University, Beijing 100084, China Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4939593

Efficiency droop is currently one of the most popular research problems for GaN-based light-emitting diodes(LEDs). In this work, a differential carrier lifetime measurement system is optimized to accurately determine carrier lifetimes (τ) of blue and green LEDs under different injection current (I). By fitting the τ-I curves and the efficiency droop curves of the LEDs according to the ABC carrier rate equation model, the impact of Auger recombination and carrier leakage on efficiency droop can be characterized simultaneously. For the samples used in this work, it is found that the experimental τ-I curves cannot be described by Auger recombination alone. Instead, satisfactory fitting results are obtained by taking both carrier leakage and carriers delocalization into account, which implies carrier leakage plays a more significant role in efficiency droop at high injection level.

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GROUP 2 - Laser and Coherent Light Group leader: Bruno Gayral (CEA)

Information selected by Knowmade

Milliwatt-class GaN-based blue vertical-cavity surface-emitting lasers fabricated by epitaxial lateral overgrowth Department of Compound Semiconductor Development, Semiconductor Device Development Division, Sony Corporation, Atsugi, Kanagawa, Japan Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532759

We have achieved continuous-wave (CW) operation of gallium nitride (GaN)-based vertical-cavity surface-emitting lasers (VCSELs) fabricated by epitaxial lateral overgrowth (ELO) using dielectric distributed Bragg reflectors (DBRs) as masks for selective growth. The GaN VCSELs exhibited CW operation at a wavelength of 453.9 nm, and the maximum output power was 1.1 mW, which is the highest value reported to date. GaN-based materials have presented challenges for obtaining DBRs with high reflectivity and a wide stopband, precise control of the cavity length and a lateral confinement structure to provide laser operation. The proposed VCSEL is immune to these concerns. Its two dielectric DBRs were obtained free from cracks. A high reflectance of more than 99.9% and a stopband with a width of 80–97 nm were obtained for both DBRs. The cavity length was controlled by epitaxial growth to as short as 4.5 µm. An ITO contact electrode on p-type GaN, which is required for a lateral confinement structure, showed electrical reliability under a high current density of 59.6 kA cm−2. The present data demonstrate that the fabrication process adopted here overcomes the shortcomings that have prevented the widespread use of GaN-based VCSELs.

Estimation of roughness-induced scattering losses in III-nitride laser diodes with a photoelectrochemically etched current aperture Department of Materials, University of California, Santa Barbara, CA, USA Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532540

We estimate the roughening-induced scattering optical losses in III-nitride current aperture laser diodes (CA-LDs) caused by imperfect photoelectrochemical (PEC) etching of the active region of a inline image InGaN multi quantum well (MQW) laser diode. Roughness data were obtained by atomic force microscope (AFM) and scanning electron microscope (SEM) image processing of the remnant PEC-etched waveguides after the top p-layers were removed by focused ion beam cuts. Roughness (correlation length) values of ∼60 (∼600) nm have been measured that cause optical loss in the range of ∼8 cm−1 as estimated by using the 3D volume current method (VCM). Larger and more irregular bends contribute more significantly to the scattering loss. Extraction of the roughness (red line) from one edge of the remnant photoelectrochemical (PEC) etched active region of current aperture laser diode (CA-LD) by image processing after the p-epilayers were removed by focused ion beam (FIB). Nanoscale Investigation of Degradation and Wavelength Fluctuations in InGaN-based Green Laser Diodes Carlo De Santi is with the Department of Information Engineering, University of Padova, Padova, Italy Nanotechnology, IEEE Transactions on http://dx.doi.org/10.1109/TNANO.2016.2520833

We present a study of the optical inhomogeneities and degradation of InGaN-based green laser diodes based on high resolution cathodoluminescence (CL) investigation of the

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output facets and inner cross-section of the devices. The results indicate that (i) degradation originates from a diffusion process, which causes an increase in the threshold current. (ii) nanoscalelevel CL points out the circular symmetry of the degraded area, which is wider than the ridge and includes not only the quantum wells but also the waveguiding and cladding layers. (iii) the yellow luminescence decreases within the degraded region, whereas its intensity increases outside of the degraded region. (iv) Wavelength fluctuations are found in both quantum wells and waveguides, which are critically analyzed and ascribed to inhomogeneity in indium concentration. Their possible effect in the filamentation of the laser emission is discussed. The role of defects in lowering the effective polariton temperature in electric and optically pumped polariton lasers Center for Photonics and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, 1301 Beal Avenue, Ann Arbor, Michigan 48109, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940401

The role of dislocations and defects in the material constituting the active region of an exciton-polariton laser has been examined and elucidated in the context of dynamic condensation and the temperature of the lower polariton condensate, TLP. For a GaNmicrocavity diode polariton laser operated at room temperature and characterized in this study, the value of TLP obtained from analysis of measured occupation in momentum space is 270 K, which is lower than the lattice temperature. Similar results from other room temperatureGaN devices and GaAs-based polariton lasers operated at cryogenic temperatures are presented and discussed.

Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture Materials Department, University of California, Santa Barbara, California 93106, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940380

We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC)etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PECetch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PECetch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm2 (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of 417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP12,1), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture.

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GANEX | Newsletter No. 37 - III-N Technology 10

GaN hemispherical micro-cavities Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940375

GaN-based micro-dome optical cavities supported on Si pedestals have been demonstrated by dry etching through gradually shrinking microspheres followed by wet-etch undercutting. Optically pumped whispering-gallery modes (WGMs) have been observed in the near-ultraviolet within the mushroom-like cavities, which do not support Fabry-Pérot resonances. The WGMs blue-shift monotonously as the excitation energies are around the lasing threshold. Concurrently, the mode-hopping effect is observed as the gain spectrum red-shifts under higher excitations. As the excitation energy density exceeds ∼15.1 mJ/cm2, amplified spontaneous emission followed by optical lasing is attained at room temperature, evident from a super-linear increase in emission intensity together with linewidth reduction to ∼0.7 nm for the dominant WGM. Optical behaviors within these WGMmicrocavities are further investigated using numerical computations and three-dimensional finite-difference time-domain simulations.

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GROUP 3 - Power Electronics Group leader: Frédéric Morancho (LAAS-CNRS)

Information selected by Frédéric Morancho (LAAS-CNRS) and Yvon Cordier (CRHEA-CNRS)

The Impact of Defects on GaN Device Behavior: Modeling Dislocations, Traps, and Pits Synopsys Inc., Mountain View, California 94043, USA Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA ECS J. Solid State Sci. Technol. http://dx.doi.org/10.1149/2.0211604jss

We demonstrate that modeling bulk traps and passivation/barrier interface traps in AlGaN/GaN HEMT is necessary to reproduce experimentally observed device behavior. Comparative modeling analysis of different leakage mechanisms in vertical p-n diode with a threading dislocation shows that variable range hopping is the dominant leakage mechanism there. The 3D quantum transport analysis of the impact of threading dislocations on electron mobility for sheet-like and nanowire-like GaN and Si MOSFET channels suggests considerable nanosheet variability and super-sensitive nanowire response. The analysis of voids in electrochemically induced pitting characterizes the impact of different pit types on different key metrics of transistor performance. Ultralow reverse leakage current in AlGaN/GaN lateral Schottky barrier diodes grown on bulk GaN substrate State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China Applied Physics Express http://dx.doi.org/10.7567/APEX.9.031001

We report on a study of AlGaN/GaN heterostructure lateral Schottky barrier diodes (L-SBDs) grown on a bulk GaN substrate. The L-SBDs exhibited an ultralow reverse leakage current below 10−6 A/cm2 without employing any extra treatments, which was over 4 orders of magnitude lower than that of a reference device on a sapphire substrate. The superior performance was attributed to the high crystalline

quality of the heterostructure achieved by homoepitaxy. The comparison also revealed that the absence of high-density trap states in the homoepitaxial L-SBD grown on the bulk GaN substrate played a key role in achieving a low reverse leakage current. Gate stack engineering for GaN lateral power transistors Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong Semiconductor Science and Technology http://dx.doi.org/10.1088/0268-1242/31/2/024001

Developing optimal gate-stack technology is a key to enhancing the reliability and performance of GaN insulated-gate devices for high-voltage power switching applications. In this paper, we discuss current challenges and review our recent progresses in gate-stack technology development toward high-performance and high-reliability GaN power devices, including (1) interface engineering that creates a high-quality dielectric/III-nitride interface with low trap density; (2) barrier-layer engineering that enables optimal trade-off between performance and stability; (3) bulk quality and reliability enhancement of the gate dielectric. These gate-stack techniques in terms of new process development and device structure design are valuable to realize highly reliable and competitive GaN power devices. Dual trench AlGaN/GaN HEMT on SiC substrate: A novel device to improve the breakdown voltage and high power performance Electrical and Computer Engineering Department, Semnan University, Semnan, Iran Physica E: Low-dimensional Systems and Nanostructures http://dx.doi.org/10.1016/j.physe.2016.01.034

In this paper, an excellent performance AlGaN/AlN/GaN/SiC High Electron Mobility

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Transistor (HEMT) with a dual trench technique (DT-HEMT) is proposed. In the proposed technique, the dual trench between the buffer layer and the nucleation layer is created. Both the trenches are made of Gallium Nitride. A trench is created under the source region to increase the breakdown voltage. In addition, the drain current will improve due to a created trench in below the gate region. The DC and RF characteristics of the DT-HEMT are investigated. Also, the characteristics of the proposed structure compared with the characteristics of a conventional structure (C-HEMT). Our results indicate that the dual trench technique has excellent impacts on the device characteristics, especially on the drain current, breakdown voltage, and maximum output power density. The breakdown voltage, drain current, and maximum power density of DT-HEMT structure improve 56%, 52%, and 310% in comparison with the C-HEMT, respectively. Also, using the dual trench technique, the maximum oscillation frequency, maximum available gain, short channel effect, maximum DC transconductance, and output resistance of the DT-HEMT structure will increase. Therefore, the proposed HEMT structure shows outstanding electrical properties compared to similar devices are based on conventional structures. Investigation of breakdown properties in the carbon doped GaN by photoluminescence analysis School of Microelectronics, Sun Yat-Sen University, Xin-Gang-Xi Rd. 135, 510275 Guangzhou, P.R. China Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510176

The electrical and optical properties of the carbon doped GaN grown on Si substrate by metal-organic chemical-vapor deposition are investigated. Carbon impurity doping can improve the breakdown voltage effectively. However excess carbon in contrast depresses the breakdown voltage. This result is correlated with the carbon dopant behaviour in GaN which can be observed by analyzing the photoluminescence (PL) spectra. It is explained that the carbon impurity favours the formation of CN (carbon

substitution of nitrogen) which acts as a deep level acceptor. The acceptor compensates the n-type background impurities, which may resulting in suppressing the leakage current at high electric field, and leads to the improvement of the breakdown voltage. However, with excess carbon doping level, a significant amount of CGa (carbon substitution of gallium) form in GaN. The CGa, acting as the donor, compensates the CN and hence impairs the concentration of the deep level acceptor. In a result, the compensation of the n-type background impurities by the deep level acceptor is curbed by the CGa-CN self-compensation effect, which leads to the decrease of the breakdown voltage. Comparison of silicon, SiC and GaN power transistor technologies with breakdown voltage rating from 1.2 kV to 15 kV Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180, USA Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510200

In recent years, different power transistors have been developed in silicon carbide (SiC) and gallium nitride (GaN) as replacements for silicon based IGBTs. This paper presents a simulation comparison of the static and dynamic performance of silicon IGBTs with different SiC and GaN based lateral and vertical power transistors (HEMT, MOSFET and IGBT) with breakdown voltage ratings between 1.2 kV to 15 kV. The strengths and weaknesses of different technologies which make them suitable at different voltage levels have been discussed. MOCVD growth of DH-HEMT buffers with low-temperature AlN interlayer on 200 mm Si (111) substrate for breakdown voltage enhancement Imec vzw, Kapeldreef 75, 3001 Leuven, Belgium Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510280

In this work, we have systematically investigated the technique of low-temperature AlN interlayer in MOCVD growth of double heterojunction high-electron-mobility transistors buffer stacks on 200 mm Si (111) substrates. We have demonstrated

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GANEX | Newsletter No. 37 - III-N Technology 13

that a continuous compressive stress can be maintained by insertion of interlayers which compensated a large tensile stress during cooling for a thick buffer. This eventually led to a low wafer bow and a good surface quality that enabled wafers with full device stack meeting the specifications for processing in our 200 mm CMOS pilot line. We also demonstrated at both forward and reverse bias conditions a significantly improved vertical buffer breakdown voltage (which is defined at a leakage current of 1 µA/mm2 in the present work) of >500 V at 25 °C and >300 V at 150 °C, respectively. High-resistance GaN-based buffer layers grown by a polarization doping method Semiconductor Lighting R&D Center, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, P.R. China Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510181

A high-resistance buffer layer is critical for GaN-based high electron mobility transistors (HEMTs) to suppress the drain leakage current and pre-mature device breakdown. A typical method to obtain the HR buffer layers is the acceptor impurity doping that is able to provide holes to compensate the background electrons in the buffer layers. However, the intentional doped acceptor impurities such as Mg, Fe and C will result in current collapse in GaN-based HEMTs. To address this issue, in this work, we employed a polarization doping method of holes by Al-composition grading instead of the acceptor impurity doping. The sheet resistance of the GaN-based buffer layer significantly increased due to the holes generated by the polarization field. Above 2000 V breakdown voltage at 600 K GaN-on-silicon high electron mobility transistors Institute of Electronic, Microelectronic and Nanotechnology, Avenue Poincare, Villeneuve d'Ascq, France Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532572

We report a three-terminal breakdown voltage over 3 kV on AlGaN/GaN high electron mobility

transistors (HEMTs) grown on 6-in. silicon (111) substrate with a buffer thickness of 5.5 μm. A local substrate removal all around the drain of the transistors has been developed in order to suppress the parasitic substrate conduction, which enables improving the device breakdown voltage by more than 200%. This establishes a new record breakdown voltage for GaN-on-silicon lateral power devices while maintaining a low-specific on-resistance of about 10 m Ω cm2. Furthermore, the device performance has been investigated at elevated temperature up to 600 K under high vacuum. Breakdown voltages well above 2 kV at temperatures exceeding 300 °C have been achieved for the first time owing to the suppression of the buffer layer/Silicon substrate parasitic conduction. These data demonstrates that the local substrate removal is not only an efficient solution to significantly boost the device breakdown voltage but also allows improving the high voltage operation under high temperature, which is a key feature for high power electronic applications. High breakdown voltage p–n diodes on GaN on sapphire by MOCVD Deptartment of ECE, University of California Santa Barbara, California, CA, USA Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532554

In order to achieve high breakdown voltage in GaN vertical power devices, low threading dislocation density and low background carrier concentration is required. This work demonstrates a decrease in the background carrier concentration and threading dislocation density (TDD) with an increase in the thickness of un-intentionally doped (UID) GaN grown on sapphire. p–n diodes grown and fabricated on this epi, using 4.8 µm UID GaN, showed a breakdown voltage of 730 V, breakdown field of 1.75 MV cm−1 and an on-resistance of 5.1 m Ω cm2. The figure of merit (FOM), VBR2/RON, thus obtained is approximately 105 MW cm−2. This is the highest reported FOM value for p–n diodes on GaN on sapphire or Si. Lowering the carrier concentration and dislocation density is thus shown to be critical for achieving high breakdown voltages on GaN on sapphire.

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GANEX | Newsletter No. 37 - III-N Technology 14

Studies on High-Voltage GaN-on-Si MIS-HEMTs Using LPCVD Si3N4 as Gate Dielectric and Passivation Layer Key Lab. of Nanodevices & Applic., Suzhou Inst. of Nano-Tech & Nano-Bionics, Suzhou, China Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2510445

This paper investigates the performance of AlGaN/gallium nitride (GaN) MIS high electron mobility transistors (MIS-HEMTs). The gate dielectric layer and the surface passivation layer are formed by the low-pressure chemical vapor deposition (LPCVD) Si3N4. The LPCVD-Si3N4 MIS-HEMTs exhibit a high breakdown voltage (BV) of 1162 V at IDS = 1 μA/mm, a low OFF-state leakage of 7.7 × 10-12 A/mm, and an excellent ON/OFF-current ratio of ~1011. Compared with the static ON-resistance of 2.88 mΩ · cm2, the dynamic ON-resistance after high OFF-state drain bias stress at 600 V only increases to 4.89 mΩ · cm2. The power device figure of merit = BV2/RON.sp is calculated to be 469 MW · cm-2. The LPCVD-Si3N4/GaN interface state density is in the range of (1.4-5.3) × 1013 eV-1 cm-2 extracted by the conventional conductance method. Finally, the gate insulator degradation of GaN-based MIS-HEMTs is analyzed by time-dependent dielectric breakdown test. The lifetime is extrapolated to 0.01% of failures after ten years at 300 K by fitting the data with a power law to a gate voltage of 10.1 V. The III-Nitride Double Heterostructure Revisited: Benefits for Threshold Voltage Engineering of MIS Devices GaN Device Technol., RWTH Aachen Univ., Aachen, Germany Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2509942

GaN-based devices are seen as ideal candidates for power-switching applications. For the acceptance of GaN-based devices by module designers, obtaining enhancement-mode (e-mode) behavior in GaN-based heterostructure field-effect transistors (HFETs) has long been in the focus. Although the gate-injection approach appears to be the most promising one to achieve e-mode devices, using a double heterostructure in

conjunction with a gate insulator has still its advantages, such as steeper turn-ON characteristics and lower leakage currents. An analytical expression to predict the threshold voltage Vth for a given double heterostructure device has not yet been derived. Moreover, neither an evaluation of the tradeoff between Vth and ON-state resistance Rds,ON has been performed to date. This paper addresses these two aspects. We will show an analytical expression for a metal-insulator-semiconductor double HFET (MIS-DHFET), which in certain cases is also valid for the gate-injection transistor. On the basis of this, we will discuss the actual influence of the Al concentration in the backbarrier on Vth. We will further employ technology computer aided design (TCAD) device simulations to evaluate the impact on Rds,ON when using MIS-DHFETs. It will be shown that by implementing a double heterostructure in MIS devices, it is possible to suppress the typically observed negative Vth-oxide thickness relationship while maintaining a constant Rds,ON. Compatibility of AlN/SiNx Passivation with LPCVD-SiNx Gate Dielectric in GaN-Based MIS-HEMT Mengyuan Hua is with the Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Kowloon, Hong Kong Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2016.2519680

In this work, we demonstrate an integrated process that illustrates the compatibility of AlN/SiNx passivation with high-performance (i.e. low leakage and high breakdown) low-pressure chemical vapor deposition (LPCVD) SiNx gate dielectric for GaN-based MIS-HEMT. It is shown that the AlN/SiNx passivation structure maintains its superior capability of suppressing the current collapse after enduring high temperature of 780 oC during the LPCVD-SiNx deposition. The AlN/SiNx passivation is shown to be significantly better than the LPCVD-SiNx passivation by delivering small dynamic RON degradation, especially under high drain bias switching with VDS > 100 V.

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GANEX | Newsletter No. 37 - III-N Technology 15

Performance Optimization of Au-Free Lateral AlGaN/GaN Schottky Barrier Diode With Gated Edge Termination on 200-mm Silicon Substrate IMEC, Leuven 3001, Belgium, and also with the Department of Electrical Engineering-Microelectronics and Sensors, KU Leuven, Leuven 3001, Belgium Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2016.2515566

In this paper, a further leakage reduction of AlGaN/GaN Schottky barrier diodes with gated edge termination (GET-SBDs) has been achieved by optimizing the physical vapor deposited TiN as the anode metal without severe degradation of ON-state characteristics. The optimized GET-SBD multifinger power diodes with 10 mm anode width deliver ~4 A at 2 V and show a median leakage of 1.3 μA at 25 °C and 3.8 μA at 150 °C measured at a reverse voltage of -200 V. The temperature-dependent leakage of Si, SiC, and our GaN power diodes has been compared. The breakdown voltage (BV) of GET-SBDs was evaluated by the variation of anode-to-cathode spacing (LAC) and the length of field plate. We observed a saturated BV of ~600 V for the GET-SBDs with LAC larger than 5 μm. The GET-SBD breakdown mechanism is shown to be determined by the parasitic vertical leakage current through the 2.8 μm-thick buffer layers measured with a grounding substrate. Furthermore, we show that the forward voltage of GET-SBDs can be improved by shrinking the lateral dimension of the edge termination due to reduced series resistance. The leakage current shows no dependence on the layout dimension LG (from 2 to 0.75 μm) and remains at a value of ~10 nA/mm. The optimized Au-free GET-SBD with low leakage current and improved forward voltage competes with high-performance lateral AlGaN/GaN SBDs reported in the literature. Normally OFF GaN-on-Si MIS-HEMTs Fabricated With LPCVD-SiNx Passivation and High-Temperature Gate Recess State Key Lab. of Electron. Thin Films & Integrated Devices, Univ. of Electron. Sci. & Technol. of China, Chengdu, China Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2510630

Low-current-collapse normally OFF GaN-on-Si MIS high-electron-mobility transistors (MIS-HEMTs) are fabricated with low-pressure chemical-vapor-deposited SiNx (LPCVD-SiNx) passivation and high-temperature low-damage gate-recess technique. The high-thermal-stability LPCVD-SiNx enables a passivation-prior-to-ohmic process strategy and effectively suppresses deep states at the passivation/HEMT interface. The fabricated MIS-HEMTs feature a high VTH of +0.85 V at the drain current of 1 μA/mm and a remarkable ON/OFF current ratio of 1010 while reduced dynamic ON-resistance as compared to plasma-enhanced chemical-vapor-deposited SiO2 passivation. High field-effect channel mobility of 180 cm2/V·s is achieved, leading to a high maximum drain current density of 663 mA/mm. Measurement of Temperature in GaN HEMTs by Gate End-to-End Resistance Technol. Qualification Group, Boeing Network & Space Syst., El Segundo, CA, USA Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2510610

We have used the gate end-to-end (GEE) resistance method to measure channel temperatures in GaN HEMTs. This method is appealing for its simplicity and sensitivity to temperature immediately adjacent to the base of the gate, where several important degradation mechanisms occur. This region is not normally accessible with optical measurement techniques, due to shadowing by the gate and field plate overhangs; yet, it is considerably hotter than the regions that can be reached with optics. We found agreement with a finite-difference model, with reasonable inputs for the thermal barrier resistance at the SiC-GaN interface and temperature coefficients. We repeated this successfully for a second GaN HEMT technology with a very different gate geometry. Finally, we conducted micro-Raman measurements on FETs from the first technology and found excellent agreement with the GEE measurement, once it had been adapted to the more-distant location of the micro-Raman laser spot, by means of our finite-difference model. We conclude that GEE is a

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GANEX | Newsletter No. 37 - III-N Technology 16

valuable tool, complementary to micro-Raman, for calibrating thermal models. An Experimental Demonstration of GaN CMOS Technology Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2016.2515103

This letter reports the first demonstration of Gallium Nitride (GaN) Complementary Metal-Oxide-Semiconductor (CMOS) field-effect-transistor (FET) technology. Selective area epitaxy was employed to have both GaN N-channel MOSFET (NMOS) and P-channel MOSFET (PMOS) structures on the same wafer. An AlN/SiN dielectric stack grown by Metal-Organic Chemical Vapor Deposition (MOCVD) served as the gate “oxide” for both NMOS and PMOS, yielding enhancement-mode N- and P-channel with the electron mobility of 300 cm2/V-sec and hole mobility of 20 cm2/V-sec, respectively. Using the GaN CMOS technology, a functional inverter Integrated Circuit (IC) was fabricated and characterized. AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with reduced leakage current and enhanced breakdown voltage using aluminum ion implantation Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123, People's Republic of China Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4939508

This letter has studied the performance of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors on silicon substrate with GaN buffer treated by aluminumion implantation for insulating followed by a channel regrown by metal–organic chemical vapor deposition. For samples with Alion implantation of multiple energies of 140 keV (dose: 1.4 × 1014 cm−2) and 90 keV (dose: 1 × 1014 cm−2), the OFF-state leakage current is decreased by more than 3

orders and the breakdown voltage is enhanced by nearly 6 times compared to the samples without Alion implantation. Besides, little degradation of electrical properties of the 2D electron gas channel is observed where the maximum drain current IDSmax at a gate voltage of 3 V was 701 mA/mm and the maximum transconductance gmmax was 83 mS/mm.

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GANEX | Newsletter No. 37 - III-N Technology 17

GROUP 4 - Advanced Electronics and RF Group leader: Jean-Claude Dejaeger (IEMN)

Information selected by Jean-Claude Dejaeger (IEMN) and Yvon Cordier (CRHEA-CNRS)

Physics of dynamic threshold voltage and steep subthreshold swing in Al2O3–InAlN–GaN MOSHEMTs State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, People's Republic of China National Key Laboratory of ASIC, Hebei Semiconductor Research Institute, Shijiazhuang, 050051, People's Republic of China Semiconductor Science and Technology http://dx.doi.org/10.1088/0268-1242/31/3/035005

The impact of Al2O3–InAlN interface traps on the switching characteristics of Al2O3–InAlN–GaN MOSHEMTs was examined using temperature-dependent current–voltage characterization. A steep subthreshold swing (SS) as low as 37 mV/dec at 25 °C is obtained, and shows negative temperature dependence up to 180 °C. We attribute this behavior to the dynamic threshold voltage (V th) induced by the de-trapping of the acceptor-like interface traps near the InAlN conduction-band edge, which acts as a positive feedback in increasing the drain current during the switch-on process. At elevated temperature, the thermally activated de-trapping of the deeper traps results in a more sufficient dynamic shift in V th and then leads to a steeper SS. The traps contributing to the steep SS were found within the energy levels ranging from E C − 0.55 to E C − 0.833 eV for the measured temperature range (25–180 °C). On the other hand, the interface traps near the midgap or at deeper energy levels act as quasi-fixed charges, which feature negligible impact on the switching behavior of the device. A comparison of the 60Co gamma radiation hardness, breakdown characteristics and the effect of SiN x capping on InAlN and AlGaN HEMTs for space applications Nitride Materials Group, Tyndall National Institute, University College Cork, Cork, Ireland

School of Engineering, University College Cork, Cork, Ireland Semiconductor Science and Technology http://dx.doi.org/10.1088/0268-1242/31/2/025008

Electrical performance and stability of InAlN and AlGaN high electron mobility transistors (HEMTs) subjected 9.1 mrad of 60Co gamma radiation and off-state voltage step-stressing until breakdown are reported. Comparison with commercially available production-level AlGaN HEMT devices, which showed negligible drift in DC performance throughout all experiments, suggests degradation mechanisms must be managed and suppressed through development of advanced epitaxial and surface passivation techniques in order to fully exploit the robustness of the III-nitride material system. Of the research level devices without dielectric layer surface capping, InAlN HEMTs exhibited the greater stability compared with AlGaN under off-state bias stressing and gamma irradiation in terms of their DC characteristics, although AlGaN HEMTs had significantly higher breakdown voltages. The effect of plasma-enhanced chemical vapour deposition SiN x surface capping is explored, highlighting the sensitivity of InAlN HEMT performance to surface passivation techniques. InAlN–SiN x HEMTs suffered more from trap related degradation than AlGaN–SiN x devices in terms of radiation hardness and step-stress characteristics, attributed to an increased capturing of carriers in traps at the InAlN/SiN x Impact of fluorine plasma treatment on AlGaN/GaN high electronic mobility transistors by simulated and experimental results School of Advanced Materials and Nanotechnology, Xidian University, 2 South Taibai Road, 710071 Xi'an, PR China Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, Xidian University, 2 South Taibai Road, 710071 Xi'an, PR China

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GANEX | Newsletter No. 37 - III-N Technology 18

Microelectronic Engineering http://dx.doi.org/10.1016/j.mee.2016.01.027

This paper demonstrates the effect of fluorine plasma treatment on the performance of AlGaN/GaN high electronic mobility transistors. The impact of ion implantation depth on threshold voltage is simulated using the Silvaco software. The simulated results declare that fluorine ions neutralize the positive polarization charge at AlGaN/GaN interface and weaken the polarization electric field. Experimental results confirm that a larger shift of threshold voltage will be achieved at a higher induced fluorine plasma bias voltage, due to the increasing depth of ion implantation. The fluorine plasma treatment is also found to be effective in lowering the gate reverse leakage current and enhance the Schottky barrier height of the metal gate. The influence of fluorine ions on the Schottky barrier height only counts for a small portion of the large shift in threshold voltage. Evidence for causality between GaN RF HEMT degradation and the EC-0.57 eV trap in GaN Electrical and Computer Engineering, The Ohio State University, Columbus, OH 43210, USA Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.11.007

The degradation of industry-supplied GaN high electron mobility transistors (HEMTs) subjected to accelerated life testing (ALT) is directly related to increases in concentrations of two defects with trap energies of EC-0.57 and EC-0.75 eV. Pulsed I-V measurements and constant drain current deep level transient spectroscopy were employed to evaluate the quantitative impact of each trap. The trap concentration increases were only observed in devices that showed a 1 dB drop in output power and not the result of the ALT itself indicating that these traps and primarily the EC-0.57 eV trap are responsible for the output power degradation. Increases from the EC-0.57 eV level were responsible for 80% of the increased knee walkout while the EC-0.75 eV contributed only 20%. These traps are located in the drain access region, likely in the GaN buffer, and cause increased knee walkout after the application of drain voltage.

Leakage Current Mechanism of InN-Based Metal-Insulator-Semiconductor Structures with Al2O3 as Dielectric Layers Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan, 430072, People’s Republic of China Nanoscale Research Letters http://dx.doi.org/10.1186/s11671-016-1232-0

InN-based metal-insulator-semiconductor (MIS) structures were prepared with Al2O3 as the gate oxides. Surface morphologies of InN films are improved with increasing Mg doping concentrations. At high frequencies, the measured capacitance densities deviate from the real ones with turning frequencies inversely proportional to series resistances. An ultralow leakage current density of 1.35 × 10−9 A/cm2 at 1 V is obtained. Fowler-Nordheim tunneling is the main mechanism of the leakage current at high fields, while Schottky emission dominates at low fields. Capacitance densities shift with different biases, indicating that the InN-based MIS structures can serve as potential candidates for MIS field-effect transistors. Study of threshold voltage instability in E-mode GaN MOS-HEMTs STMicroelectronics, Stradale Primosole 50, 95121 Catania, Italy Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510191

In this work, the threshold instability in E-mode GaN MOS-HEMTs was investigated. In particular, the shift of VTH as a function of the applied positive gate voltage during device characterization was monitored, resulting in positive VTH shifts up to 1 V. A complete VTH recovery required more than one day of unbiased storage, but a partial recovery of the observed VTH shift was observed after few seconds. These results could be related to different positions of trap states: fast states, localized at the dielectric/GaN interface and slow states, the traps inside the dielectric layer. Moreover, VTH shift of 0.2 and 0.8 V for fast and slow states, respectively, was obtained. To gain insight into the physical

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GANEX | Newsletter No. 37 - III-N Technology 19

mechanism involved in the observed phenomena, numerical simulation were also carried out. A VTH shift was obtained adding the interface states. Moreover, three different distributions of traps were compared. In particular, the concentration of filled traps was monitored to understand the impact of the distribution on the electrical behaviour. An increment in filled trap concentration at the increasing of the applied VGS, which in turns correlates with experimentally evaluated device behaviour, was obtained if the distribution of traps states is also above the GaN conduction band energy. Modulation of the domain mode in GaN-based planar Gunn diode for terahertz applications The State Key Discipline Laboratory of Wide Band Gap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, P.R. China Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510158

This paper reports the modulation of the domain mode in the 2DEG channel of GaN HEMT-like Gunn diodes by adjustment the electron concentration of the 2DEG near the cathode side. The enhancement of the electron concentration near the cathode side promotes the fast formation of the dipole domain layer and greatly reduces the dead zone length, which increases the RF output power. The employment of the recess layer near the cathode reduces the electron concentration of the 2DEG beneath it, which acts as a notch-doped layer as in the bulk vertical diode. The reduction of the electron concentration of the 2DEG near the cathode promotes the formation of dual-domain in one oscillation circle, which aims to enhance harmonic components of Gunn oscillation so as to minimize the use of frequency multipliers for SMMW and THz operation. Analysis of threshold voltage instability in AlGaN/GaN MISHEMTs by forward gate voltage stress pulses NaMLab gGmbH, Dresden, Germany Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532756

We report on the investigation of the Vth drift behaviour of AlGaN/GaN MISHEMTs upon forward gate voltage stress in dependence of stress bias and stress time. The pulsed measurements allow for the evaluation of the operational regime for optimum device efficiency. We compared the effect of two different high-κ gate dielectric materials with similar equivalent oxide thickness ϵ0ϵr/thigh-κ on the Vth instability in order to separate the influence of the heterojunction design and the high-κ/GaN-cap interface from the bulk high-κ. The matched gate capacitance coupling of the studied Al2O3 and HfO2 gate dielectric results in an nearly identical critical forward gate voltage, where the AlGaN barrier potential is lowered and severe threshold voltage shift (ΔVth) into the positive voltage direction is induced. Beyond this critical forward voltage, detailed time-dependent stress pulse measurements from 1 µs to 1000 s revealed an immediate electron injection and trapping at the oxide/GaN interface for stress pulses with tstress ≥ 1 µs. The presented results of Vth drift analysis demonstrate the limits of the maximum tolerable forward gate voltage of the investigated Al2O3 and HfO2 MISHEMTs, although the excellent low-leakage currents of the insulated gate would imply a potentially higher gate-overdrive. Direct observation of nanometer-scale gate leakage paths in AlGaN/GaN and InAlN/AlN/GaN HEMT structures Fujitsu Laboratories Ltd., Atsugi, Kanagawa, Japan Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532547

This paper investigates the effects of MOVPE growth parameters on the gate leakage characteristics of InAlN HEMT structures and compares leakage current paths in AlGaN and InAlN HEMT structures on a nanometer scale. The gate leakage characteristics of AlGaN and InAlN HEMT were compared, and the large leakage current in InAlN HEMT was found to result from the high-density 2DEG-induced strong electric field accumulation in the barrier layer. Both the increasing growth rate and decreasing growth temperature in the InAIN layer of InAlN HEMT

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GANEX | Newsletter No. 37 - III-N Technology 20

caused the deterioration of gate leakage characteristics and surface morphologies. Conductive AFM measurements were performed for AlGaN and InAlN HEMT structures, and a one-to-one clear correlation between surface pits and leakage paths was found for AlGaN HEMT. On the contrary, for the InAlN HEMT grown at a low temperature, high-density localized leakage paths were observed. We believe the observed leakage paths originate from nanometer-scale material fluctuations, which is most likely an indium composition fluctuation. Our results indicate that it is necessary to grow the InAlN barrier layer at 740 °C or higher and that the growth rate must be 1.25 nm min−1 or less to realize low-gate leakage in InAlN HEMT. A further reduction of the gate leakage current requires the reduction of the dislocation density and use of gate insulators. Normally OFF GaN-on-Si MIS-HEMTs Fabricated With LPCVD-SiNx Passivation and High-Temperature Gate Recess State Key Lab. of Electron. Thin Films & Integrated Devices, Univ. of Electron. Sci. & Technol. of China, Chengdu, China Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2510630

Low-current-collapse normally OFF GaN-on-Si MIS high-electron-mobility transistors (MIS-HEMTs) are fabricated with low-pressure chemical-vapor-deposited SiNx (LPCVD-SiNx) passivation and high-temperature low-damage gate-recess technique. The high-thermal-stability LPCVD-SiNx enables a passivation-prior-to-ohmic process strategy and effectively suppresses deep states at the passivation/HEMT interface. The fabricated MIS-HEMTs feature a high VTH of +0.85 V at the drain current of 1 μA/mm and a remarkable ON/OFF current ratio of 1010 while reduced dynamic ON-resistance as compared to plasma-enhanced chemical-vapor-deposited SiO2 passivation. High field-effect channel mobility of 180 cm2/V·s is achieved, leading to a high maximum drain current density of 663 mA/mm.

>70% Power-added-efficiency Dual-gate, Cascode GaN HEMTs without Harmonic Tuning HRL Laboratories, Malibu, CA 90265 USA Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2016.2520488

We report state-of-the-art performance of deep-submicron gate length dual-gate GaN HEMTs and cascode GaN HEMTs with 10X reduced gate-to-drain feedback capacitance compared to single-gate GaN HEMTs. With 150-nm gate length field-plated gate structures, these GaN HEMTs demonstrated improvement of small-signal gain by 10 dB, compared to single-gate GaN HEMTs. Large-signal load-pull measurements showed peak power-added-efficiency of 71% – 74% without harmonic tuning at 10 GHz, up to a measured continuous-wave output power level of 2.3 – 2.5 W. The 74% power-added-efficiency is very close to a theoretical maximum power-added-efficiency of 78.5% without harmonic tuning. Compared to singlegate GaN HEMTs, both the dual-gate and cascode GaN HEMTs offer ~10% improvement in peak PAE at the output power of 2.3 – 2.5 W. Measurement of Temperature in GaN HEMTs by Gate End-to-End Resistance Technol. Qualification Group, Boeing Network & Space Syst., El Segundo, CA, USA Electron Devices, IEEE Transactions on http://dx.doi.org/10.1109/TED.2015.2510610

We have used the gate end-to-end (GEE) resistance method to measure channel temperatures in GaN HEMTs. This method is appealing for its simplicity and sensitivity to temperature immediately adjacent to the base of the gate, where several important degradation mechanisms occur. This region is not normally accessible with optical measurement techniques, due to shadowing by the gate and field plate overhangs; yet, it is considerably hotter than the regions that can be reached with optics. We found agreement with a finite-difference model, with reasonable inputs for the thermal barrier resistance at the SiC-GaN interface and temperature coefficients. We repeated this successfully for a second GaN HEMT technology with a very different gate geometry. Finally, we

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GANEX | Newsletter No. 37 - III-N Technology 21

conducted micro-Raman measurements on FETs from the first technology and found excellent agreement with the GEE measurement, once it had been adapted to the more-distant location of the micro-Raman laser spot, by means of our finite-difference model. We conclude that GEE is a valuable tool, complementary to micro-Raman, for calibrating thermal models. A top-gate GaN nanowire metal–semiconductor field effect transistor with improved channel electrostatic control ISOM-ETSIT, Universidad Politécnica de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940197

A uniformly n-type dopedGaN:Si nanowire (NW), with a diameter of d = 90 nm and a length of 1.2 μm, is processed into a metal-semiconductor field effect transistor (MESFET) with a semi-cylindrical top Ti/Au Schottky gate. The FET is in a normally-ON mode, with the threshold at −0.7 V and transconductance of gm ∼ 2 μS (the transconductance normalized with NW diameter gm/d > 22 mS/mm). It enters the saturation mode at VDS ∼ 4.5 V, with the maximum measured drain current IDS = 5.0 μA and the current density exceeding JDS > 78 kA/cm2. Demonstration of InAlN/AlGaN high electron mobility transistors with an enhanced breakdown voltage by pulsed metal organic chemical vapor deposition Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, People's Republic of China Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4939689

In this work, InAlN/AlGaN heterostructures employing wider bandgap AlGaN instead of conventional GaN channel were grown on sapphire substrate by pulsed metal organic chemical vapor deposition, where the nominal Al composition in InAlN barrier and AlGaN channel were chosen to be 83% and 5%, respectively, to

achieve close lattice-matched condition. An electron mobility of 511 cm2/V s along with a sheet carrier density of 1.88 × 1013 cm−2 were revealed in the prepared heterostructures, both of which were lower compared with lattice-matched InAlN/GaN due to increased intrinsic alloy disorder scattering resulting from AlGaN channel and compressively piezoelectric polarization in barrier, respectively. While the high electron mobility transistor(HEMT) processed on these structures not only exhibited a sufficiently high drain output current density of 854 mA/mm but also demonstrated a significantly enhanced breakdown voltage of 87 V, which is twice higher than that of reported InAlN/GaN HEMT with the same device dimension, potential characteristics for high-voltage operation of GaN-based electronic devices.

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GANEX | Newsletter No. 37 - III-N Technology 22

GROUP 5 – MEMS and Sensors Group leader: Marc Faucher (IEMN)

Information selected by Marc Faucher (IEMN)

Local residual stress monitoring of aluminum nitride MEMS using UV micro-Raman spectroscopy The Pennsylvania State University, University Park, PA 16802, USA Sandia National Laboratories, Albuquerque, NM 87123, USA Journal of Micromechanics and Microengineering http://dx.doi.org/10.1088/0960-1317/26/2/025009

Localized stress variation in aluminum nitride (AlN) sputtered on patterned metallization has been monitored through the use of UV micro-Raman spectroscopy. This technique utilizing 325 nm laser excitation allows detection of the AlN E2(high) phonon mode in the presence of metal electrodes beneath the AlN layer with a high spatial resolution of less than 400 nm. The AlN film stress shifted 400 MPa from regions where AlN was deposited over a bottom metal electrode versus silicon dioxide. Across wafer stress variations were also investigated showing that wafer level stress metrology, for example using wafer curvature measurements, introduces large uncertainties for predicting the impact of AlN residual stress on the device performance. Ultraviolet photoresponse of ZnO nanostructured AlGaN/GaN HEMTs Division of Electronics and Electrical Engineering, Dongguk University, 100-715 Seoul, Republic of Korea Materials Science in Semiconductor Processing http://dx.doi.org/10.1016/j.mssp.2016.01.004

We present the first active visible blind ultraviolet (UV) photodetector based on zinc oxide (ZnO) nanostructured AlGaN/GaN high electron mobility transistors (HEMTs). The ZnO nanorods (NRs) are selectively grown on the gate area by using hydrothermal method. It is shown that ZnO nanorod (NR)-gated UV detectors exhibit much superior performance in terms of response speed and recovery time to those of seed-layer-gated detectors. It is also found that the best response

speed (~10 and~190 ms) and responsivity (~1.1×105 A/W) were observed from detectors of the shortest gate length of 2 µm among our NR-gated devices of three different gate dimensions, and this responsivity is about one order higher than the best performance of ZnO NR-based UV detectors reported to date. InGaN/GaN core/shell nanowires for visible to ultraviolet range photodetection Institut d'Electronique Fondamentale, UMR CNRS 8622, Université Paris Sud 11, Orsay, France Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532573

We report on the fabrication and characterization of single nitride nanowire visible-to-ultraviolet p–n photodetectors. Nitride nanowires containing 30 InGaN/GaN radial quantum wells with 18% indium fraction were grown by catalyst-free metal-organic vapour phase epitaxy. Single nanowires were contacted using optical lithography. As expected for a radial p–n junction, the current–voltage (I–V) curves of single wire detectors show a rectifying behavior in the dark and a photocurrent under illumination. The detectors present a response in the visible to UV spectral range starting from 2.8 eV. The peak responsivity is 0.17 A/W at 3.36 eV. The on-off switching time under square light pulses is found to be below 0.1 s. Wavelength-Specific Ultraviolet Photodetectors Based on AlGaN Multiple Quantum Wells Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Kolkata, India Quantum Electronics, IEEE Journal of http://dx.doi.org/10.1109/JQE.2016.2516445

The detection of a specific spectral line in ultraviolet in the presence of broadband ambient lighting is necessary for many applications. We report wavelength-selective photodetection using AlGaN multiple quantum wells grown by

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molecular beam epitaxy. A near-Gaussian photoresponse peak at 300 nm with a width of 17 nm was achieved in the lateral photocurrent, along with a much faster transient response compared with the devices based on bulk AlGaN. The wavelength selectivity, controlled by the formation and subsequent splitting of excitons, was achieved by the optimization of the alloy properties of the barrier layers, reducing the leakage of photogenerated carriers into the active region. Influence of Au based metallization on the phase velocity of GaN on Si Surface Acoustic Wave resonators Alexandra Stefanescu is with the IMT-Bucharest, 32B Erou Iancu Nicolae, R-07719, Bucharest, Romania Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2016.2521431

This letter presents a comparison between the phase velocity of Al and Ti/Au metalized GaN/Si based Surface Acoustic Wave (SAW) structures. The resonance frequency (and consequently the phase velocity) is higher for Ti/Au based metallization, especially when the acoustic wavelength has comparable values with the GaN layer thickness. Simulation results are in excellent agreement with the experiment. For example, the phase velocity on 1 μm thin GaN layer with 200 nm finger/interdigit spacing width of the interdigitated transducer (IDT) is 3707 m/s (simulated value: 3840 m/s) for 100 nm thin Al metallization and 4360 m/s (simulated value: 4240 m/s) for Ti/Au 5 nm /95 nm thin metallization. This behavior was explained considering the effects of the significantly higher value of the acoustic impedance of Au compared with Al. The simulated mode shapes have confirmed this explanation. The advantage of the Ti/Au metallization lies in the possibility to obtain a higher resonance frequency for the same topology of the IDT.

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GANEX | Newsletter No. 37 - III-N Technology 24

GROUP 6 - Photovoltaics and Energy harvesting Group leader: Eva Monroy (INAC-CEA)

Information selected by Knowmade

Design of nitride semiconductors for solar energy conversion National Renewable Energy Laboratory, Golden, USA J. Mater. Chem. A http://dx.doi.org/10.1039/C5TA09446A

Nitride semiconductors are a promising class of materials for solar energy conversion applications, such as photovoltaic and photoelectrochemical cells. Nitrides can have better solar absorption and electrical transport properties than the more widely studied oxides, as well as the potential for better scalability than other pnictides or chalcogenides. In addition, nitrides are also relatively unexplored compared to other chemistries, so they provide a great opportunity for new materials discovery. This paper reviews the recent advances in the design of novel semiconducting nitrides for solar energy conversion technologies. Both binary and multinary nitrides are discussed, with a range of metal chemistries (Cu3N, ZnSnN2, Sn3N4, etc.) and crystal structures (delafossite, perovskite, spinel, etc.), including a brief overview of wurtzite III-N materials and devices. The current scientific challenges and promising future directions in the field are also highlighted. Influence of the inverse Auger process on the performance of InxGa1−xN/GaN quantum dot solar cells Azar Aytash Co., Technology Incubator, University of Tabriz, Tabriz, Iran Optik - International Journal for Light and Electron Optics http://dx.doi.org/10.1016/j.ijleo.2016.01.156

It has been proposed that the use of self-assembled nano sized quantum dot (QD) arrays can break the Shockley–Queisser efficiency limit by extending the absorption of solar cells into the low-energy photon range while preserving their output voltage. This would be possible if the infrared photons are absorbed in the two sub-

bandgap QD transitions simultaneously and the energy of two photons is added up to produce one single electron–hole pair, as described by the intermediate band model. This paper indicates the energy conversion efficiency of a quantum dot multilayer solar cell considering impact ionization effect. A p–i–n InxGa1−xN/GaN quantum dot solar cell structure has been taken into account in the calculation. It is shown that the efficiency of a cell strongly depends on the impact ionization in stacked quantum dots at i-region of the cell. In our proposed structure it is demonstrated that, if averaged probability of impact ionization, P, varies from zero to one, maximum efficiency increases by more than 12% (from 43 percent in P = 0 to 55 percent in P = 1). Also it is demonstrated that by decreasing θ, maximum efficiency increases and reaches to its maximum, 59%, in θ = 2. Effect of an ITO current spreading layer on the performance of InGaN MQW solar cells Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, United Kingdom Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510171

InGaN-based solar cells have been investigated through fabrication with and without using an indium-tin-oxide (ITO) current spreading layer (CSL). For the devices with a planar top surface, utilization of the ITO CSL leads to enhanced performance under 1 sun air-mass 1.5 global spectrum illumination. In contrast, when surface-texturing is applied to significantly improve the light absorption, the efficiency of the device without using the ITO CSL is higher compared to the one with the ITO. Furthermore, measurements on reflectance of the corresponding surfaces and transmission of the ITO CSL are carried out. The influence of the ITO CSL has been discussed in terms of surface reflection, the light loss due to the ITO CSL shading and the power loss associated with the absence of the ITO CSL.

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GANEX | Newsletter No. 37 - III-N Technology 25

Theoretical analysis of the influence of band tail defects on PIN InGaN solar cells School of Information Science and Engineering, Hebei University of Science and Technology, 26 Yuxiang Street, 050000 Shijiazhuang, Hebei Province, P.R. China Institute of Semiconductors, Chinese Academy of Sciences, PO Box 912, 10083 Beijing, P.R. China Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510198

InGaN solar cells have higher conversion efficiency than traditional Si based solar cells. However, efficiency of experimental InGaN solar cell is lower than expected. There are still several problems, such as the structure design of InGaN solar cells, the quality of InGaN materials, need to be discussed and solved. Thus, the researches of structure design and defect effects are important for the implications of InGaN solar cells. The performance of p-GaN/i-InxGa1–x/n-GaN solar cells with different In content is simulated by AMPS-1D. It is found that the optimum efficiency of p-GaN/i-InxGa1–xN/n-GaN solar cells is 8.9% when the In content is 0.26. The p-GaN/i-In0.26Ga0.74/n-GaN solar cells with band tail defects are simulated. The simulated results show the efficiency decreases with the increase of the E-character. And the efficiency decreases sharply from 8.30% to 7.19% when the capture cross section is 10–14 cm–2. Proposal of leak path passivation for InGaN solar cells to reduce the leakage current Center for SMART Green Innovation Research, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940970

We propose some general ways to passivate the leak paths in InGaNsolar cells and report some experimental evidences of its effectiveness. By adopting an AlOx passivation process, the photovoltaic performances of GaN pn-junctions and InGaNsolar cells,grown by molecular beam epitaxy, have been significantly improved. The open circuit voltage under 1 sun illumination increases from 1.46 to 2.26 V for a GaN pn

junction, and from 0.95 to 1.27 V for an InGaNsolar cell, demonstrating evidence of leak path passivation(LPP) by AlOx. The proposed LPP is expected to be a realistic way to exploit the potential of thick and relaxed but defective InGaN for solar cell applications.

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GANEX | Newsletter No. 37 - III-N Technology 26

GROUP 7 - Materials, Technology and Fundamental Group leader: Jean-Christophe Harmand (LPN-CNRS)

NANO

Information selected by Jean-Christophe Harmand (LPN-CNRS)

Highly elongated vertical GaN nanorod arrays on Si substrates with an AlN seed layer by pulsed-mode metal–organic vapor deposition Department of Electrical Engineering and Computer Science, Nagoya University, Nagoya, Japan CrystEngComm http://dx.doi.org/10.1039/C5CE02056E

To extend the availability of nanostructure-based optoelectronic applications, vertically elongated nanorods with precisely controlled morphology are required. For group III nitrides, pulsed-mode growth has recently been reported as an effective method for growing nanorod arrays with geometric precision. Here, we demonstrated the growth of arrays of highly elongated nanorods on Si substrates by metal–organic chemical vapor deposition using a pulsed-mode approach. Unlike the thick and high (or middle)-quality GaN templates normally used, nanorod growth was performed on an ultrathin and low-quality AlN/Si platform. Using kinetically controlled growth conditions and a patterning process, exceptionally long GaN nanorods were achieved with high geometric precision. The grown nanorods showed considerably improved optical and structural properties while remaining in uniform arrays. This approach can be used with a variety of materials to obtain nanorods with high quality, high uniformity, and high aspect ratio, and it can also serve as an effective fabrication method for InAlGaN-alloyed core/shell nanostructures for optoelectronic nanodevices with ultrahigh efficiency. Nanogenerators based on vertically aligned InN nanowires Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Ave. West, Waterloo, Canada

Nanoscale http://dx.doi.org/10.1039/C5NR06841J

Piezoelectric nanogenerators (NGs) based on vertically aligned InN nanowires (NWs) are fabricated, characterized, and evaluated. In these NGs, arrays of p-type and intrinsic InN NWs prepared by plasma-assisted molecular beam epitaxy (MBE) demonstrate similar piezoelectric properties. The p-type NGs show 160% more output current and 70% more output power product than the intrinsic NGs. The features driving performance enhancement are reduced electrostatic losses due to better NW array morphology, improved electromechanical energy conversion efficiency due to smaller NW diameters, and the higher impedance of intrinsic NGs due to elevated NW surface charge levels. These findings highlight the potential of InN based NGs as a power source for self-powered systems and the importance of NW morphology and surface state in overall NG performance. Enhancing UV-emissions through optical and electronic dual-function tunings of Ag nanoparticles hybridized with n-ZnO nanorods/p-GaN heterojunction light-emitting diodes Institute of Electro-Optical Science and Technology, National Taiwan Normal University, 88, Sec.4, Ting-Chou Road, Taipei 116, Taiwan Nanoscale http://dx.doi.org/10.1039/C5NR08561F

ZnO nanorods (NRs) and Ag nanoparticles (NPs) are known for enhancing the luminescence of light-emitting diodes (LEDs) through high directionality of waveguide mode transmission and efficient energy transfer of localized surface plasmon (LSP) resonances, respectively. In this work, we demonstrated Ag NPs-incorporated n-ZnO NRs/p-GaN heterojunctions by facilely hydrothermally growing ZnO NRs on Ag NPs-covered GaN, in which the Ag NPs were introduced and randomly distributed on the p-GaN surface to excite the LSP resonances. Compared with the reference LED, the light-out

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power of the near-band-edge (NBE) emission (ZnO, λ=380 nm) of our hybridized structure is increased almost 1.5−2 times and can be further modified in a controlled manner by varying the surface morphology of the surrounding medium of the Ag NPs. The improved light-output power is mainly attributed to the LSP resonance between the NBE emission of ZnO NRs and LSPs in Ag NPs. We also observed different behavior in the electroluminescence (EL) spectra as the injection current increased for the treatment and reference LEDs. This observation might be attributed to the modification of the energy band diagram for introducing Ag NPs at the interface between n-ZnO NRs and p-GaN. Our results pave the way for developing advanced nanostructured LED devices with high luminescence efficiency in the UV emission regime. Germanium-catalyzed growth of single-crystal GaN nanowires CINTRA – CNRS/NTU/Thales, UMI 3288, 50 Nanyang Drive, 637553, Singapore School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2015.12.051

We report the use of Germanium (Ge) as catalyst for Gallium Nitride (GaN) nanowires growth. High-yield growth has been achieved with Ge nanoparticles obtained by dewetting a thin layer of Ge on a Si (100) substrate. The nanowires are long and grow straight with very little curvature. The GaN nanowires are single-crystalline and show a Wurtzite structure growing along the [0001] axis. The growth follows a metal-free Vapor–Liquid–Solid (VLS) mechanism, further allowing a CMOS technology compatibility. The synthesis of nanowires has been done using an industrial Low Pressure Chemical Vapor Deposition (LPCVD) system. Quantum Dot-Like Behavior of Compositional Fluctuations in AlGaN Nanowires Univ. Grenoble Alpes, F-38000 Grenoble, France CEA, INAC-PHELIQS, “Nanophysics and Semiconductors” Group, F-38000 Grenoble, France

Nano Lett. http://dx/doi.org/10.1021/acs.nanolett.5b03904

We report on the structural and optical properties of AlxGa1–xN nanowire sections grown by plasma-assisted molecular beam epitaxy on GaN nanowire bases used as a template. Based on a combination of scanning electron microscopy, microphotoluminescence, time-resolved microphotoluminescence, and photon correlation experiments, it is shown that compositional fluctuations in AlxGa1–xN sections associated with carrier localization optically behave as quantum dots. Moreover, most of the micro-optical properties of such fluctuations are demonstrated to be very little dependent on kinetic growth parameters such as AlxGa1–xN growth temperature and AlN molar fraction in the alloy, which govern the macrostructural properties of AlxGa1–xN sections. Facile Formation of High-Quality InGaN/GaN Quantum-Disks-in-Nanowires on Bulk-Metal Substrates for High-Power Light-Emitters Photonics Laboratory, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia Nano Lett. http://dx.doi.org/10.1021/acs.nanolett.5b04190

High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light-emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrates. The LEDs exhibited a low turn-on voltage of ∼2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm2) at ∼5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride

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(TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector, and heat sink, which greatly simplifies the fabrication process of high-power light-emitters. Our work ushers in a practical platform for high-power nanowires light-emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates. Polar, semi- and non-polar nitride-based quantum dots: influence of substrate orientation and material parameter sets on electronic and optical properties Tyndall National Institute, Lee Maltings, Cork, Ireland Department of Physics, University College Cork, Cork, Ireland Optical and Quantum Electronics http://dx.doi.org/10.1007/s11082-016-0426-0

In this work we present a detailed analysis of electrostatic built-in fields, electronic and optical properties of InGaN-based quantum dots grown on different crystallographic planes. The calculations are performed by means of a symmetry adapted k⋅p model. Special attention is paid to the influence of different effective mass and deformation potential parameter sets on the results. Our analysis reveals that the built-in potential profile is strongly dependent on the growth plane. These changes in the built-in potential affect the electronic structure and therefore the optical properties of semi-polar InGaN quantum dots significantly. For instance, while we observe a clear spatial separation of electron and hole ground state wave functions for quantum dots grown on the (101¯3)-plane, for the (202¯1)-plane our results indicate a strong spatial overlap. Furthermore, we show that the calculation of the degree of optical linear polarization in the considered semipolar InGaN quantum dot systems significantly depends on the chosen material parameter set for substrate incline angles of 0∘<θ<58∘. For instance, for

growth on the (101¯3) (θ=32∘)-plane, the degree of optical linear polarization changes from 90 to 10 % when changing the input material parameter set. InGaN/GaN core/shell nanowires for visible to ultraviolet range photodetection Institut d'Electronique Fondamentale, UMR CNRS 8622, Université Paris Sud 11, Orsay, France Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532573

We report on the fabrication and characterization of single nitride nanowire visible-to-ultraviolet p–n photodetectors. Nitride nanowires containing 30 InGaN/GaN radial quantum wells with 18% indium fraction were grown by catalyst-free metal-organic vapour phase epitaxy. Single nanowires were contacted using optical lithography. As expected for a radial p–n junction, the current–voltage (I–V) curves of single wire detectors show a rectifying behavior in the dark and a photocurrent under illumination. The detectors present a response in the visible to UV spectral range starting from 2.8 eV. The peak responsivity is 0.17 A/W at 3.36 eV. The on-off switching time under square light pulses is found to be below 0.1 s. III-nitride microcrystal cavities with quasi whispering gallery modes grown by molecular beam epitaxy Ioffe Institute, 26 Politekhnicheskaya, St Petersburg 194021, Russia Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552657

This paper analyzes current trends in fabrication of III-nitride microresonators exploiting whispering gallery modes. Novel cup-cavities are proposed and their fabrication from GaN and InN by molecular beam epitaxy on patterned substrates is described. These cup-cavities can concentrate the mode energy in a subwavelength volume. Their mode energies are stable up to room temperature, being identical in large microcrystals. In these cavities, mode switching can be realized by means of refractive index variation. Cup-cavity modes, being inferior to

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plasmonic resonances in the respect of integral emission enhancement, have advantages for spectrally selective amplification of quantum transitions in site-controlled nano-emitters. A physical model for the reverse leakage current in (In,Ga)N/GaN light-emitting diodes based on nanowires Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, D-10117 Berlin, Germany J. Appl. Phys. http://dx.doi.org/10.1063/1.4940949

We investigated the origin of the high reverse leakage current in light emitting diodes(LEDs) based on (In,Ga)N/GaN nanowire (NW) ensembles grown by molecular beam epitaxy on Si substrates. To this end, capacitance deep level transient spectroscopy(DLTS) and temperature-dependent current-voltage (I-V) measurements were performed on a fully processed NW-LED. The DLTSmeasurements reveal the presence of two distinct electron traps with high concentrations in the depletion region of the p-i-n junction. These band gap states are located at energies of 570 ± 20 and 840 ± 30 meV below the conduction band minimum. The physical origin of these deep level states is discussed. The temperature-dependent I-V characteristics, acquired between 83 and 403 K, show that different conduction mechanisms cause the observed leakage current. On the basis of all these results, we developed a quantitative physical model for chargetransport in the reverse bias regime. By taking into account the mutual interaction of variable range hopping and electron emission from Coulombic trap states, with the latter being described by phonon-assisted tunnelling and the Poole-Frenkel effect, we can model the experimental I-V curves in the entire range of temperatures with a consistent set of parameters. Our model should be applicable to planar GaN-based LEDs as well. Furthermore, possible approaches to decrease the leakage current in NW-LEDs are proposed.

Counterintuitive strain distribution in axial (In,Ga)N/GaN nanowires Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin, Germany Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940053

We study the three-dimensional deformation field induced by an axial (In,Ga)N segment in a GaNnanowire. Using the finite element method within the framework of linear elasticity theory, we study the dependence of the strain field on the ratio of segment length and nanowire radius. Contrary to intuition, the out-of-plane-component εzzεzz of the elastic strain tensor is found to assume large negative values for a length-to-radius ratio close to one. We show that this unexpected effect is a direct consequence of the deformation of the nanowire at the free sidewalls and the associated large shear strain components. Simulated reciprocal space maps of a single (In,Ga)N/GaN nanowire demonstrate that nanofocus x-ray diffraction is a suitable technique to assess this peculiar strain state experimentally. A top-gate GaN nanowire metal–semiconductor field effect transistor with improved channel electrostatic control ISOM-ETSIT, Universidad Politécnica de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940197

A uniformly n-type dopedGaN:Si nanowire (NW), with a diameter of d = 90 nm and a length of 1.2 μm, is processed into a metal-semiconductor field effect transistor (MESFET) with a semi-cylindrical top Ti/Au Schottky gate. The FET is in a normally-ON mode, with the threshold at −0.7 V and transconductance of gm ∼ 2 μS (the transconductance normalized with NW diameter gm/d > 22 mS/mm). It enters the saturation mode at VDS ∼ 4.5 V, with the maximum measured drain current IDS = 5.0 μA and the current density exceeding JDS > 78 kA/cm2.

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GANEX | Newsletter No. 37 - III-N Technology 30

NON/SEMI POLAR Information selected by

Philippe De Mierry (CRHEA-CNRS) Rotation of in-plane structural anisotropy at the interface of a-plane InN/GaN heterostructure grown by MOCVD on r-plane sapphire Institute of Materials Research and Engineering (IMRE), A*STAR Agency for Science, Technology and Research, 3 Research Link, Singapore 117602, Singapore CrystEngComm http://dx.doi.org/10.1039/C5CE02595H

We have epitaxially grown InN thin films on c- and r-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD) using GaN buffers. Their structural and optical comparisons revealed high quality for the a-plane InN/GaN heterostructure on r-plane sapphire. Remarkable in-plane structural anisotropy, which manifests itself as additional rocking curve (RC) broadenings, has been observed as usual by high-resolution x-ray diffraction (HRXRD) for both the GaN buffer and the InN overlayer; however, we observed a 90°-rotation of the anisotropy, i.e., from the M-shape for the GaN buffer to the W-shape for the InN overlayer, in the a-plane InN/GaN heterostructure. This anisotropy rotation, a hitherto unknown behavior in monolithic growth of nonpolar III-nitrides, has a strong correlation with the crystallographic tilts between the individual epilayers and the r-plane sapphire substrate in the InN/GaN heterostructure. These observations, together with the direction of the unintentional miscut (~0.09°) of the r-plane sapphire substrate, provide evidence for the effect of island coalescences on lattice tilt in epitaxial growth with large lattice mismatches. Spatially resolved and orientation dependent Raman mapping of epitaxial lateral overgrowth nonpolar a-plane GaN on r-plane sapphire Wide Bandap Semiconductor Technology Disciplines State Key Laboratory, School of Microelectronics, Xidian University, Xi’an 710071, China Scientific Reports http://dx.doi.org/10.1038/srep19955

Uncoalesced a-plane GaN epitaxial lateral overgrowth (ELO) structures have been synthesized along two mask stripe orientations on a-plane GaN template by MOCVD. The morphology of two ELO GaN structures is performed by Scanning electronic microscopy. The anisotropy of crystalline quality and stress are investigated by micro-Raman spectroscopy. According to the Raman mapping spectra, the variations on the intensity, peak shift and the full width at half maximum (FWHM) of GaN E2 (high) peak indicate that the crystalline quality improvement occurs in the window region of the GaN stripes along [0001], which is caused by the dislocations bending towards the sidewalls. Conversely, the wing regions have better quality with less stress as the dislocations propagated upwards when the GaN stripes are along []. Spatial cathodoluminescence mapping results further support the explanation for the different dislocation growth mechanisms in the ELO processes with two different mask stripe orientations. Polar, semi- and non-polar nitride-based quantum dots: influence of substrate orientation and material parameter sets on electronic and optical properties Tyndall National Institute, Lee Maltings, Cork, Ireland Department of Physics, University College Cork, Cork, Ireland Optical and Quantum Electronics http://dx.doi.org/10.1007/s11082-016-0426-0

In this work we present a detailed analysis of electrostatic built-in fields, electronic and optical properties of InGaN-based quantum dots grown on different crystallographic planes. The calculations are performed by means of a symmetry adapted k⋅p model. Special attention is paid to the influence of different effective mass and deformation potential parameter sets on the results. Our analysis reveals that the built-in potential profile is strongly dependent on the growth plane. These changes in the built-in potential affect the electronic structure and therefore the optical properties of semi-polar InGaN quantum dots significantly. For instance, while we observe a clear spatial separation of

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GANEX | Newsletter No. 37 - III-N Technology 31

electron and hole ground state wave functions for quantum dots grown on the (101¯3)-plane, for the (202¯1)-plane our results indicate a strong spatial overlap. Furthermore, we show that the calculation of the degree of optical linear polarization in the considered semipolar InGaN quantum dot systems significantly depends on the chosen material parameter set for substrate incline angles of 0∘<θ<58∘. For instance, for growth on the (101¯3) (θ=32∘)-plane, the degree of optical linear polarization changes from 90 to 10 % when changing the input material parameter set. Influence of Band Tailing on Photo- and Electroluminescence Polarization of m-Plane InGaN/GaN Quantum Well Heterostructures B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimost’ Ave., Minsk, 220072, Belarus Journal of Applied Spectroscopy http://dx.doi.org/10.1007/s10812-016-0211-7

Nonpolar m-plane InGaN/GaN light emitting diode structures with quantum well (QW) were grown on LiAlO2 (100) substrates. Their photoluminescence and electroluminescence were investigated at different excitation levels. It was shown that in QW of InGaN with the pronounced InGaN band tailing, the populating of both the first and the second valence subbands of InGaN takes place due to tunneling of charge carriers and, therefore, a lower degree of polarization of the electroluminescence was observed in comparison with photoluminescence. The differences in luminescence properties under optical and electrical excitation are discussed. Semi-polar (11-22) GaN grown on patterned (113) Si substrate Department of Electronic and Electrical Engineering, University of Sheffield, Mappin street, Sheffield S13DJ, United Kingdom Physica status solidi (c) http://dx.doi.org/10.1002/pssc.201510209

An epitaxial growth technic has been developed to synthesize semi-polar (11-22) GaN on (113) Si substrate with inverted-pyramid patterns. The

reaction between Ga and Si substrate has been successfully solved by simply depositing a thin SiO2 layer on selective regions of the substrate before growth. High quality semi-polar (11-22) GaN-on-Si with a smooth surface has been obtained after delicately tuning growth conditions. Based on the scanning electron microscopy and x-ray diffraction characterizations, a model has been well established to illuminate the growth process. Due to the very low density of defects confirmed by transmission electron microscopy, our sample demonstrates an excellent optical property, which is promising for efficient optoelectronic devices using GaN-on-Si configuration. Complete orientational access for semipolar GaN devices on sapphire Department of Electrical Engineering, Yale University, New Haven, CT, USA Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201670503

The complete freedom to choose the surface orientation of GaN has been an elusive goal for growth on sapphire substrates. As opposed to bulk GaN substrates, which can be arbitrarily sliced at any orientations, the growth on planar sapphire substrates is constrained to only several discrete orientations. For high efficiency, low droop light-emitting diodes, the surface with the best demonstrated LEDs has been a moving target, and on planes within the continuous angular-orientation space not demonstrated as of yet on sapphire substrates. In their Feature Article on pp. 23–35, Leung et al. review the advances in high performance semipolar and nonpolar GaN LEDs, providing guidance on the desired GaN surfaces. A complete process is then demonstrated to enable these unique orientations of GaN using sapphire substrates. In particular, electrically injected (20-21) GaN LEDs are fabricated on sapphire by the use of stripe-patterned substrates, inclined c-plane GaN growth and a chemical-mechanical planarization. Finally, the complete range of orientations is shown to be opened by the demonstration of an orientation (hkil), where l < 0, namely (20-2-1) GaN on

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sapphire, which has been achieved here for the first time. Study of low efficiency droop in semipolar (20-2-1) InGaN light-emitting diodes by time-resolved photoluminescence School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ 85287, U.S.A. Display Technology, Journal of http://dx.doi.org/10.1109/JDT.2016.2521618

The superior low efficiency droop performance of semipolar (2021) InGaN light-emitting diodes (LEDs) makes it a hot candidate for efficient solid-state lighting and full-color displays. To unveil the mystery of this low droop and highefficiency, the emission dynamics of semipolar (2021) LEDs is investigated by time-resolved and steady-state photoluminescence (PL) measurements. Much smaller carrier lifetimes (radiative and nonradiative lifetime) were obtained from semipolar (2021) InGaN QWs compared to those on the c-plane samples, possibly due to the reduced quantum-confined Stark effects and smaller indium fluctuation on semipolar InGaN samples. The experimental findings indicate a much reduced excess carrier density in semipolar (2021) InGaN LEDs, which will impact the device performance. Based on this, a modified ABC equation with weak phase-space-filling (PSF) effect was used to model the droop characteristics of semipolar (2021) LEDs. Multi-microscopy study of the influence of stacking faults and three-dimensional In distribution on the optical properties of m-plane InGaN quantum wells grown on microwire sidewalls Groupe de Physique des Matériaux, UMR CNRS 6634, Normandie University, INSA and University of Rouen, 76800 St Etienne du Rouvray, France Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940748

The optical properties of m-plane InGaN/GaN quantum wellsgrown on microwire sidewalls were investigated carrying out a correlative scanning transmission electron microscopy (STEM), atom

probe tomography (APT), and micro-photoluminescence study applied on single nanoscale field-emission tips obtained by a focused ion beam annular milling. Instead of assuming simple rectangular composition profiles, yielding misleading predictions for the optical transition energies, we can thus take into account actual compositional distributions and the presence of stacking faults (SFs). SFs were shown to be responsible for a lowering of the recombination energies of the order of 0.1 eV with respect to those expected for defect-free quantum wells(QWs). Such energy reduction allows establishing a good correspondence between the transition energies observed by optical spectroscopy and those calculated on the basis of the QWs In measured composition and distribution assessed by STEMstructuralanalysis and APT chemical mapping. Nonpolar III-nitride vertical-cavity surface-emitting laser with a photoelectrochemically etched air-gap aperture Materials Department, University of California, Santa Barbara, California 93106, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940380

We demonstrate a III-nitride nonpolar vertical-cavity surface-emitting laser (VCSEL) with a photoelectrochemically (PEC)etched aperture. The PEC lateral undercut etch is used to selectively remove the multi-quantum well (MQW) region outside the aperture area, defined by an opaque metal mask. This PEC aperture (PECA) creates an air-gap in the passive area of the device, allowing one to achieve efficient electrical confinement within the aperture, while simultaneously achieving a large index contrast between core of the device (the MQW within the aperture) and the lateral cladding of the device (the air-gap formed by the PECetch), leading to strong lateral confinement. Scanning electron microscopy and focused ion-beam analysis is used to investigate the precision of the PECetch technique in defining the aperture. The fabricated single mode PECA VCSEL shows a threshold current density of ∼22 kA/cm2 (25 mA), with a peak output power of ∼180 μW, at an emission wavelength of

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417 nm. The near-field emission profile shows a clearly defined single linearly polarized (LP) mode profile (LP12,1), which is in contrast to the filamentary lasing that is often observed in III-nitride VCSELs. 2D mode profile simulations, carried out using COMSOL, give insight into the different mode profiles that one would expect to be displayed in such a device. The experimentally observed single mode operation is proposed to be predominantly a result of poor current spreading in the device. This non-uniform current spreading results in a higher injected current at the periphery of the aperture, which favors LP modes with high intensities near the edge of the aperture. Stokes shift in semi-polar (112¯2112¯2) InGaN/GaN multiple quantum wells Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, United Kingdom Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940396

The mechanism for the large Stokes Shifts of InGaN/GaN structures is under debate. Here, we report a systematic study on the Stokes shift of semi-polar (112¯2112¯2) InGaN/GaN multiple quantum wells(MQWs) with a wide spectral range from green (490 nm) to yellow (590 nm) by means of both photoluminescence excitation and time resolved PL measurements in comparison with their c-plane counterparts. The semi-polar samples exhibit a lower Stokes shift than their c-plane counterparts, although they show stronger localization effect than their c-plane counterparts. In the long wavelength region, the Stokes shift of the semi-polar MQWs shows a linear relationship with emission energy, but with a smaller gradient compared with their c-plane counterparts. The time-resolved PL measurements confirm a significant reduction in piezoelectric field of the semi-polar samples compared with the c-plane counterparts. It is suggested that the piezoelectric field induced polarization is the major mechanism for causing the large Stokes shift. The presented results contribute to better understanding of the long standing issue on the mechanism for the large Stokes shift.

Critical thickness for the formation of misfit dislocations originating from prismatic slip in semipolar and nonpolar III-nitride heterostructures ITMO University, St. Petersburg 197101, Russia APL Mater. http://dx.doi.org/10.1063/1.4939907

We calculate the critical thickness for misfit dislocation (MD) formation in lattice mismatched semipolar and nonpolar III-nitride wurtzite semiconductor layers for the case of MDs originated from prismatic slip (PSMDs). It has been shown that there is a switch of stress relaxation modes from generation of basal slip originated MDs to PSMDs after the angle between c-axis in wurtzite crystal structure and the direction of semipolar growth reaches a particular value, e.g., ∼70° for Al0.13Ga0.87N/GaN (h0h 1h0h 1) semipolar heterostructures. This means that for some semipolar growth orientations of III-nitride heterostructures biaxial relaxation of misfit stress can be realized. The results of modeling are compared to experimental data on the onset of plastic relaxation in AlxGa1−xN/GaN heterostructures.

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Agnès Trassoudaine (Université d'Auvergne) and Yvon Cordier (CRHEA-CNRS)

Kinetic Analysis of GaN-MOVPE via Thickness Profiles in the Gas Flow Direction with Systematically Varied Growth Conditions Department of Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan ECS J. Solid State Sci. Technol. http://dx.doi.org/10.1149/2.0071603jss

We carried out a kinetic analysis of metallorganic vapor phase epitaxy (MOVPE) of GaN to investigate the dependence of the growth rate on the process conditions as a function of residence time of the precursors in the reactor. The wafer was not rotated during growth, allowing us to analyze the thickness profile of the film in the direction of gas flow, and hence the dependence

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of the growth rate on the residence time. The growth rate is determined mainly by the concentration of the growth species and mass transfer of the growth species to the wafer surface. The growth rate peaked in the flow direction, and the position of this peak could, in most cases, be explained by considering a combination of the linear gas velocity and the time constant for vertical diffusion of trimethylgallium (TMGa) and/or growth species across the NH3 feed stream to the wafer surface. In some cases this was not possible, indicating that more complex effects were significant. This work is expected to contribute to understanding of the reaction pathways for GaN-MOVPE, and the growth rate data reported here are expected to provide useful benchmarks for growth simulations that combine computational fluid dynamics and reaction models. Energy relaxation of hot electrons in III-N bulk materials State Key Discipline Laboratory of Wide Bandgap Semiconductor Technologies, School of Microelectronics, Xidian University, Xi'an 710071, People's Republic of China Semiconductor Science and Technology http://dx.doi.org/10.1088/0268-1242/31/2/025016

Energy relaxation of the hot electrons in GaN, AlN and InN is investigated and compared based on a simple analytical model with both the hot-phonon effect (HPE) and the nonparabolicity of the conduction band taken into account. The impact of the HPE on the energy relaxation time is estimated by using various optical phonon lifetimes. The calculation results show that for this group of III nitrides, the energy relaxation time first falls rapidly and then saturates with the increasing electron temperature, and is higher at a high electron density. The presence of the HPE slows down the power dissipation and increases the energy relaxation time of the hot electrons of the density 1 × 1018 cm−3 (or 1 × 1019 cm−3) by around one or two orders of magnitude at an electron temperature within 3000 K. In particular, the saturated energy relaxation times are 0.12 ps in the bulk GaN, 22 fs in AlN and 26 fs in InN for an

electron density of 1 × 1018 cm−3, which imply a rather weak HPE in the AlGaN and AlInN alloys. Strong impact of the initial III/V ratio on the crystalline quality of an AlN layer grown by rf-plasma-assisted molecular-beam epitaxy Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan Applied Physics Express http://dx.doi.org/10.7567/APEX.9.025502

The initial Al/N ratio for AlN growth of plasma-assisted molecular-beam epitaxy without plasma stabilization is investigated. The in situ growth rate of AlN gradually increased and its temporal variation corresponded to that of nitrogen atoms, which indicated that the initial Al/N ratio was excessively Al-rich. For AlN growth, such a high-Al/N-ratio condition resulted in a three-dimensional growth mode in the initial stage of the growth, and AlN with high threading dislocation density was obtained. By controlling the initial Al/N ratio by introducing a short standby time, the resulting two-dimensional initial growth mode leads to high-quality growth of AlN. Annealing of an AlN buffer layer in N2–CO for growth of a high-quality AlN film on sapphire Graduate School of Regional Innovation Studies, Mie University, Tsu 514-8507, Japan Department of Electrical and Electronic Engineering, Mie University, Tsu 514-8507, Japan Applied Physics Express http://dx.doi.org/10.7567/APEX.9.025501

The annealing of an AlN buffer layer in a carbon-saturated N2–CO gas on a sapphire substrate was investigated. The crystal quality of the buffer layer was significantly improved by annealing at 1650–1700 °C. An AlN buffer layer with a thickness of 300 nm was grown by metalorganic vapor phase epitaxy (MOVPE), and was annealed at 1700 °C for 1 h. We fabricated a 2-µm-thick AlN layer on the annealed AlN buffer layer by MOVPE. The full widths at half maximum of the (0002)- and ($10\bar{1}2$)-plane X-ray rocking curves were 16 and 154 arcsec, respectively, and the threading dislocation density was 4.7 × 108 cm−2.

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Silicon doping of HVPE GaN bulk-crystals avoiding tensile strain generation NaMLab gGmbH, Nöthnitzer Straße 64, D-01187 Dresden, Germany Journal of Physics D: Applied Physics http://dx.doi.org/10.1088/0022-3727/49/7/075502

Doped GaN:Si crystals were grown in a commercially available vertical HVPE reactor. The templates used for the HVPE heteroepitaxy were so-called FACELO seeds, with a starting GaN layer thickness of 3–4 μm. The FWHM of the 0002 and the $30\bar{3}2$ reflection of the HVPE-grown GaN:Si crystals with a thickness of 3 mm are ${{31}^{\prime\prime}}$ and ${{78}^{\prime\prime}}$ , respectively, indicating excellent crystal quality. Hall measurements resulted in a charge carrier concentration of $1.5\times {{10}^{18}}$ cm−3, while exhibiting a mobility of 250 cm−2V−1 s−1. These values coincide with the values extracted from FTIR measurements and the lineshape fitting of the A1(LO)/plasmon coupled phonon mode of the confocal Raman measurements. SIMS investigations yielded a silicon atom concentration of $1.8\times {{10}^{18}}$ cm−3. This indicates an activation of the dopant atoms of approximately 90%. The TDD determined by CL dark spot counting was $2\times {{10}^{6}}$ cm−2. Within the measurement accuracy, the confocal Raman measurements did not show a tensile strain generation due to the silicon doping with resulting charge carrier concentrations of $1.5\times {{10}^{18}}$ cm−3. Metalorganic chemical vapor deposition and characterization of (Al,Si)O dielectrics for GaN-based devices Materials Department, University of California, Santa Barbara, CA 93106, U.S.A. Japanese Journal of Applied Physics http://dx.doi.org/10.7567/JJAP.55.021501

In this paper, we report on the growth and electrical characterization of (Al,Si)O dielectrics grown by metalorganic chemical vapor deposition (MOCVD) using trimethylaluminum, oxygen, and silane as precursors. The growth rates, refractive indices, and composition of (Al,Si)O films grown

on Si(001) were determined from ellipsometry and XPS measurements. Crystallinity and electrical properties of (Al,Si)O films grown in situ on c-plane GaN were characterized using grazing incidence X-ray diffraction and capacitance–voltage with current–voltage measurements, respectively. Si concentration in the films was found to be tunable by varying the trimethylaluminum and/or oxygen precursor flows. The Si incorporation suppressed the formation of crystalline domains, leading to amorphous films that resulted in reduced interfacial trap density, low gate leakage and ultra-low hysteresis in (Al,Si)O/n-GaN MOS-capacitors. Utilization of native oxygen in Eu(RE)-doped GaN for enabling device compatibility in optoelectronic applications Department of Physics and Astronomy, University of Mount. Union, 1972 Clark Ave, Alliance, OH, 44601, USA Scientific Reports http://dx.doi.org/10.1038/srep18808

The detrimental influence of oxygen on the performance and reliability of V/III nitride based devices is well known. However, the influence of oxygen on the nature of the incorporation of other co-dopants, such as rare earth ions, has been largely overlooked in GaN. Here, we report the first comprehensive study of the critical role that oxygen has on Eu in GaN, as well as atomic scale observation of diffusion and local concentration of both atoms in the crystal lattice. We find that oxygen plays an integral role in the location, stability, and local defect structure around the Eu ions that were doped into the GaN host. Although the availability of oxygen is essential for these properties, it renders the material incompatible with GaN-based devices. However, the utilization of the normally occurring oxygen in GaN is promoted through structural manipulation, reducing its concentration by 2 orders of magnitude, while maintaining both the material quality and the favorable optical properties of the Eu ions. These findings open the way for full integration of RE dopants for

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optoelectronic functionalities in the existing GaN platform. Intervalley scattering in hexagonal boron nitride Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, F-34095, Montpellier, France Phys. Rev. B http://dx.doi.org/10.1103/PhysRevB.93.035207

We report photoluminescence experiments bringing the evidence for intervalley scattering in bulk hexagonal boron nitride. From a quantitative analysis of the defect-related emission band, we demonstrate that transverse optical phonons at the K point of the Brillouin zone assist inter-K valley scattering, which becomes observable because stacking faults in bulk hexagonal boron nitride provide a density of final electronic states. Time-resolved experiments highlight the different recombination dynamics of the phonon replicas implying either virtual excitonic states or real electronic states in the structural defects. Mg incorporation in GaN grown by plasma-assisted molecular beam epitaxy at high temperatures Department of Electrical Engineering, National Tsing Hua University Hsinchu, Taiwan 30013, Republic of China Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.01.011

The influence of growth conditions on the incorporation and activation of Mg in GaN grown by plasma-assisted molecular beam epitaxy at high growth temperature (>700 °C) is presented. It is found that the highest Mg incorporation with optimized electrical properties is highly sensitive both to the Mg/Ga flux ratio and III/V flux ratio. A maximum Mg activation of ~5% can be achieved at a growth temperature of 750 °C. The lowest resistivity achieved is 0.56 Ω-cm which is associated with a high hole mobility of 6.42 cm2/V-s and a moderately high hole concentration of 1.7×1018 cm−3. Although the highest hole concentration achieved in a sample grown under a low III/V flux ratio and a high Mg/Ga flux ratio reaches 7.5×1018 cm−3, the

mobility is suffered due to the formation of defects by the excess Mg. In addition, we show that modulated beam growth methods do not enhance Mg incorporation at high growth temperature in contrast to those grown at a low temperature of 500 °C (Appl. Phys. Lett. 93, 172112, Namkoong et al., 2008 [19]). Controlling the compositional inhomogeneities in AlxGa1−xN/AlyGa1−yN MQWs grown by PA-MBE: Effect on luminescence properties Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, JD2 Sector III Salt Lake City, Kolkata 700098, West Bengal, India Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.01.004

Al0.35Ga0.65N/Al0.55Ga0.45N MQWs were grown by PA-MBE using a range of group III/V flux ratios. TEM images indicate sharp interfaces and well/barrier widths of 1.5/2 nm. We observe that small variations of group III/V flux ratio cause dramatic variations in the room temperature photoluminescence (PL) spectra. In addition to band edge luminescence, multiple low energy PL peaks are observed for growths under excess group III conditions, which are absent for near-stoichiometric growth. Temperature dependent PL measurements indicate that at room temperature, emission occurs due to transitions at potential fluctuations generated by the presence of compositional inhomogeneity. These effects are dominant for growth under excess group III conditions due to the presence of a metallic layer on the growth surface during deposition. This can be eliminated by the use of an Indium surfactant during growth, which modifies the diffusion length of Ga and Al adatoms. Under these conditions, the optical properties of MQWs are relatively insensitive to variations in group III to V flux ratio and hence substrate temperature, thus making them suitable for industrial-scale fabrication of optoelectronic devices in the ultraviolet range.

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Investigations of GaN growth on the sapphire substrate by MOCVD method with different AlN buffer deposition temperatures Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Rd., Hsinchu 30010, Taiwan Materials Science in Semiconductor Processing http://dx.doi.org/10.1016/j.mssp.2016.01.008

The effects of different AlN buffer deposition temperatures on the GaN material properties grown on sapphire substrate was investigated. At relatively higher AlN buffer growth temperature, the surface morphology of subsequent grown GaN layer was decorated with island-like structure and revealed the mixed-polarity characteristics. In addition, the density of screw TD and leakage current in the GaN film was also increased. The occurrence of mixed-polarity GaN material result could be from unintentional nitridation of the sapphire substrate by ammonia (NH3) precursor at the beginning of the AlN buffer layer growth. By using two-step temperature growth process for the buffer layer, the unintentional nitridation could be effectively suppressed. The GaN film grown on this buffer layer exhibited a smooth surface, single polarity, high crystalline quality and high resistivity. AlGaN/GaN high electron-mobility transistor (HEMT) devices were also successfully fabricated by using the two-step AlN buffer layer. Electron affinity of GaN(0001) surface doped with Al, Mg Department of Opto-Electric Engineering, Bingzhou University, Bingzhou 256603, China Optik - International Journal for Light and Electron Optics http://dx.doi.org/10.1016/j.ijleo.2015.12.145

Using first-principles method, we studied the electronic structures, work functions and electron affinities of the GaN(0001), Ga(Mg)N(0001), AlGa(Mg)N(0001), and Cs adsorbed AlGa(Mg)N(0001) surfaces. A method was offered to calculate the surface electron affinity using work function. The results show that Al 3s has a strong appeal to N 2s, which enhances the orbital hybridization of Mg s and N p states, and increases doping concentration. The interaction

between Mg and N atoms enhanced by Al doping leads to the increase of surface dipole moment. AlGa(Mg)N(0001)’s work function is the smallest in comparison with that of GaN(0001) and GaMgN(0001) surfaces. After Cs adsorption on AlGa(Mg)N(0001) surface, the transfer of Cs6s electrons to Ga atoms in the outermost layer enhances the dipole moment pointing to outside and decreases the work function of the system, the negative electron affinity achieves. Influence of trench period and depth on MOVPE grown View the MathML source GaN on patterned r-plane sapphire substrates. Institute of Optoelectronics, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2016.01.014

In this article, the influence of the trench period and depth of pre-structured r-plane sapphire substrates on the metalorganic vapor phase epitaxy (MOVPE) growth of View the MathML source GaN is investigated. We found that a larger trench period is beneficial for a small basal plane stacking fault (BSF) and threading dislocation (TD) density on the wafer surface, because it facilitates a better formation of a coalescence gap, which effectively blocks defects from penetrating to the surface. Further, the amount of BSFs emerging from the –c-wings of the uncoalesced GaN stripes is directly related to the trench period. With the help of in-situ deposited marker layers we studied the development of the individual GaN stripes and observed that the trench depth and hence the ratio of the sapphire c-plane area relative to the total surface area heavily influences the coalescence process and defect development. Moreover, it is observed that the parasitic donor concentration increases for samples with smoother wafer surface. State of strain in GaN material as derived by optical feedback measurement Department of Opto-electronic Engineering, College of Opto-electronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073, China

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Optik - International Journal for Light and Electron Optics http://dx.doi.org/10.1016/j.ijleo.2016.01.119

Strain in gallium nitride (GaN) leads to serious problems, such as cracks, dislocation and wafer bending. Therefore, the strain magnitude and distribution in GaN is important to understand. In this paper, we describe the state of strain in GaN materials as derived by the optical feedback technology. The tiny strain of GaN materials, including the strain distribution, is measured by using the optical feedback approach, which makes it possible to detect whether the GaN tested meets its strain requirements. Defect reduction in MBE-grown AlN by multicycle rapid thermal annealing National Research Council Postdoctoral Fellow Residing at U.S. Naval Research Laboratory, Washington, D.C., 20375, USA Electronic Materials Letters http://dx.doi.org/10.1007/s13391-015-5270-z

Multicycle rapid thermal annealing (MRTA) is shown to reduce the defect density of molecular beam epitaxially grown AlN films. No damage to the AlN surface occurred after performing the MRTA process at 1520°C. However, the individual grain structure was altered, with the emergence of step edges. This change in grain structure and diffusion of AlN resulted in an improvement in the crystalline structure. The Raman E2 linewidth decreased, confirming an improvement in crystal quality. The optical band edge of the AlN maintained the expected value of 6.2 eV throughout MRTA annealing, and the band edge sharpened after MRTA annealing at increased temperatures, providing further evidence of crystalline improvement. X-ray diffraction shows a substantial improvement in the (002) and (102) rocking curve FWHM for both the 1400 and 1520°C MRTA annealing conditions compared to the as-grown films, indicating that the screw and edge type dislocation densities decreased. Overall, the MRTA post-growth annealing of AlN lowers defect density, and thus will be a key step to improving optoelectronic and power electronic devices.

Effect of SiC-on-Si template residual stress on GaN residual stress and crystal quality Queensland Micro and Nanotechnology Centre, Griffith University, Nathan 4111, Queensland, Australia Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552626

The thermal expansion coefficient mismatch between GaN and SiC is lower than between GaN and Si. However it is usually observed that GaN on SiC/Si templates has higher tensile stress than GaN directly on Si. To provide an insight into the relationship between SiC template residual stress and GaN overlayer residual stress and crystal quality, we have analyzed the in-plane residual stress gradient present in GaN/SiC microstructure arrays of various dimensions and shapes using micro-Raman spectroscopy. It was found that the GaN overlayer residual stress is directly proportional to the SiC buffer layer residual stress. GaN films with lower residual stress also resulted in GaN films with improved crystal quality. Our study shows that the frequently encountered problems of high tensile stress in GaN films deposited on SiC templates is due to the high tensile residual stress in the SiC layers. The poorer GaN crystal quality deposited on SiC templates reported in literature is also likely due to the high tensile stress in the SiC templates. In order to grow GaN films with sufficient compressive stress and crystal quality for subsequent device processing, it is crucial to reduce the high tensile stress present in the SiC templates. Polarized Raman and photoluminescence studies of a sub-micron sized hexagonal AlGaN crystallite for structural and optical properties Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, India Journal of Raman Spectroscopy http://dx.doi.org/10.1002/jrs.4877

The polarized Raman spectroscopy is capable of giving confirmation regarding the crystalline phase as well as the crystallographic orientation of the sample. In this context, apart from crystallographic X-ray and electron diffraction tools, polarized Raman spectroscopy and corresponding spectral imaging can be a

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promising crystallographic tool for determining both crystalline phase and orientation. Sub-micron sized hexagonal AlGaN crystallites are grown by a simple atmospheric pressure chemical vapor deposition technique using the self catalytic vapor–solid process under N-rich condition. The crystallites are used for the polarized Raman spectra in different crystalline orientations along with spectral imaging studies. The results obtained from the polarized Raman spectral studies show single crystalline nature of sub-micron sized hexagonal AlGaN crystallites. Optical properties of the crystallites for different crystalline orientations are also studied using polarized photoluminescence measurements. The influence of internal crystal field to the photoluminescence spectra is proposed to explain the distinctive observation of splitting of emission intensity reported, for the first time, in case of c-plane oriented single crystalline AlGaN crystallite as compared with that of m-plane oriented crystallite. Origin of lattice bowing of freestanding GaN substrates grown by hydride vapor phase epitaxy Toyohashi University of Technology, 1-1 Hibarigaoka Tempaku, Toyohashi, Aichi 441-8580, Japan J. Appl. Phys. http://dx.doi.org/10.1063/1.4940914

This paper describes a mechanism to explain the lattice bowing of freestanding GaN substrates grown by hydride vapor phase epitaxy on sapphire substrates. The freestanding GaN substrates typically exhibit a concave shape. It is revealed that the radius of curvature and lattice constant of the top surface are almost the same as those of the bottom surface. This is indicative of the complete relaxation of the GaN lattice, even though the freestanding GaN substrate exhibited a curvature. It is shown that dislocations are present in a plane normal to the growth direction in addition to conventionally known threading dislocations; these are referred to as in-plane dislocations. Based on these results, it is proven quantitatively that the extra-half planes related to the in-plane dislocations are primarily responsible for the phenomenon of lattice bowing.

Spatial identification of traps in AlGaN/GaN heterostructures by the combination of lateral and vertical electrical stress measurements State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4941027

We present a methodology and the corresponding experimental results to identify the exact location of the traps that induce hot electron trapping in AlGaN/GaN heterostructures grown on Si substrates. The methodology is based on a combination of lateral and vertical electrical stress measurements employing three ohmic terminals on the test sample structure with different GaN buffer designs. By monitoring the evolution of the lateral current during lateral as well as vertical stress application, we investigate the trapping/detrapping behaviors of the hot electrons and identify that the traps correlated with current degradation are in fact located in the GaNbuffer layers. The trap activation energies (0.38–0.39 eV and 0.57–0.59 eV) extracted from either lateral or vertical stress measurements are in good agreement with each other, also confirming the identification. By further comparing the trapping behaviors in two samples with different growth conditions of an unintentionally dopedGaN layer, we conclude that the traps are most likely in the unintentionally dopedGaN layer but of different origins. It is suggested that the 0.38–0.39 eV trap is related to residual carbon incorporation while the 0.57–0.59 eV trap is correlated with native defects or complexes. Electrical spin injection and detection of spin precession in room temperature bulk GaN lateral spin valves Center for Photonic and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4940888

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We report the measurement of diffusive electronic spin transport characteristics in an epitaxial wurtzite GaN lateral spin valve at room temperature. Hanle spin precession and non-local spin accumulation measurements have been performed with the spin valves fabricated with FeCo/MgO spin contacts. Electron spin relaxation length and spin-flip lifetime of 176 nm and 37 ps, respectively, are derived from analysis of results obtained from four-terminal Hanle spin precession measurements at 300 K. The role of dislocations and defects in bulk GaN has also been examined in the context of electronic spin relaxation dynamics. Hydrogen-carbon complexes and the blue luminescence band in GaN Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284, USA J. Appl. Phys. http://dx.doi.org/10.1063/1.4939865

The blue luminescence band with a maximum at 3.0 eV and the zero-phonon line at 3.33 eV (labeled BL2) is observed in high-resistivity GaN. Under prolonged ultraviolet (UV) light exposure, the BL2 band transforms into the yellow luminescence (YL) band with a maximum at 2.2 eV. Our hybrid functional calculations suggest that the BL2 band is related to a hydrogen-carbon defect complex, either CNON-Hi or CN-Hi. The complex creates defect transition level close to the valence band, which is responsible for the BL2 band. Under UVillumination, the complex dissociates, leaving as byproduct the source of the YL band (CNON or CN) and interstitial hydrogen. Microscopic potential fluctuations in Si-doped AlGaN epitaxial layers with various AlN molar fractions and Si concentrations Department of Material Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan J. Appl. Phys. http://dx.doi.org/10.1063/1.4939864

Nanoscopic potential fluctuations of Si-doped AlGaNepitaxial layers with the AlN molar fraction varying from 0.42 to 0.95 and Si-doped

Al0.61Ga0.39N epitaxial layers with Si concentrations of 3.0–37 × 1017 cm−3 were investigated by cathodoluminescence(CL) imaging combined with scanning electron microscopy. The spot CLlinewidths of AlGaNepitaxial layers broadened as the AlN molar fraction was increased to 0.7, and then narrowed at higher AlN molar fractions. The experimental linewidths were compared with the theoretical prediction from the alloy broadening model. The trends displayed by our spot CLlinewidths were consistent with calculated results at AlN molar fractions of less than about 0.60, but the spot CLlinewidths were markedly broader than the calculated linewidths at higher AlN molar fractions. The dependence of the difference between the spot CLlinewidth and calculated line broadening on AlN molar fraction was found to be similar to the dependence of reported S values, indicating that the vacancy clusters acted as the origin of additional line broadening at high AlN molar fractions. The spot CLlinewidths of Al0.61Ga0.39N epitaxial layers with the same Al concentration and different Si concentrations were nearly constant in the entire Si concentration range tested. From the comparison of reported S values, the increase of VAl did not contribute to the linewidth broadening, unlike the case of the VAl clusters. Controlling a three dimensional electron slab of graded AlxGa1−xN Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstr. 69, A-4040 Linz, Austria Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4939788

Polarization induced degenerate n-type doping with electron concentrations up to ∼1020 cm−3 is achieved in graded AlxGa1−xN layers (x: 0% → 37%) grown on unintentionally doped and on n-doped GaN:Si buffer/reservoir layers by metal organic vapor phase epitaxy. High resolution x-ray diffraction, transmission electron microscopy, and electron dispersive x-ray spectroscopy confirm the gradient in the composition of the AlxGa1−xN layers, while Hall effect studies reveal the formation of a three dimensional electron slab,

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whose conductivity can be adjusted through the GaN(:Si) buffer/reservoir. Anomalous lattice deformation in GaN/SiC(0001) measured by high-speed in situ synchrotron X-ray diffraction Quantum Beam Science Center, Japan Atomic Energy Agency, 1-1-1 Koto, Sayo, Hyogo 679-5148, Japan Appl. Phys. Lett. http://dx.doi.org/10.1063/1.4939450

We report an anomalous lattice deformation of GaN layers grown on SiC(0001) by molecular beam epitaxy. The evolution of the lattice parameters during the growth of the GaN layers was measured by in situ synchrotron X-ray diffraction. The lattice parameters in the directions parallel and normal to the surface showed significant deviation from the elastic strains expected for lattice-mismatched films on substrates up to a thickness of 10 nm. The observed lattice deformation was well explained by the incorporation of hydrostatic strains due to point defects. The results indicate that the control of point defects in the initial stage of growth is important for fabricating GaN-based optoelectronic devices. Growth of free-standing wurtzite AlGaN by MBE using a highly efficient RF plasma source School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, United Kingdom J. Vac. Sci. Technol. http://dx.doi.org/10.1116/1.4940155

Ultraviolet light emitting diodes(UVLEDs) are now being developed for various potential applications including water purification, surface decontamination, optical sensing, and solid-state lighting. The basis for this development is the successful production of AlxGa1−xN UVLEDsgrown by either metal-organic vapor phase epitaxy (MOVPE) or molecular beam epitaxy(MBE). Initial studies used mainly sapphire as the substrate, but this result in a high density of defects in the epitaxialfilms and now bulk GaN or AlN substrates are being used to reduce this to acceptable values. However, the lattice parameters of GaN

and AlN are significantly different, so any AlGaN alloy grown on either substrate will still be strained. If, however, AlGaN substrates were available, this problem could be avoided and an overall lattice match achieved. At present, the existing bulk GaN and AlN substrates are produced by MOVPE and physical vapor transport, but thick free-standing films of AlGaN are difficult to produce by either method. The authors have used plasma-assisted MBE to grow free-standing AlxGa1−xN up to 100 μm in thickness using both an HD25 source from Oxford Applied Research and a novel high efficiency source from Riber to provide active nitrogen. Films were grown on 2- and 3-in. diameter sapphire and GaAs (111)B substrates with growth rates ranging from 0.2 to 3 μm/h and with AlN contents of 0% and ∼20%. Secondary ion mass spectrometer studies show uniform incorporation of Al, Ga, and N throughout the films, and strong room temperature photoluminescence is observed in all cases. For filmsgrown on GaAs, the authors obtained free-standing AlGaN substrates for subsequent growth by MOVPE or MBE by removing the GaAs using a standard chemical etchant. The use of high growth rates makes this a potentially viable commercial process since AlxGa1−xN free-standing films can be grown in a single day and potentially this method could be extended to a multiwafer system with a suitable plasma source.

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PRESS RELEASE Technical and economic information selected by Knowmade

OPTOELECTRONICS

Plessey to build LEDs in cubic GaN on Anvil Semiconductors' 3C-SiC/Si substrates to overcome The Green Gap i-micronews

Plessey, Anvil Semiconductors and the University of Cambridge announced today that they are working together to fabricate high efficiency LEDs in cubic GaN grown on Anvil's 3C-SiC / Si substrates. Cubic GaN has the potential to overcome the problems caused in conventional LEDs by the strong internal electric fields which impair carrier recombination and contribute to efficiency droop. Read more GaN-on-Si technology wins innovation award i-micronews

Shunfeng International Clean Energy (SFCE or the company) announced that its subsidiary, Lattice Power, has won the first prize of the National Science and Technology Invention Award for the «High Efficacy GaN-on-Si Blue LED» technology that was jointly developed by Lattice Power, Nanchang University, CECEP Lattice Lighting and the China Energy Conservation and Environmental Protection Group. «Currently there are three LED technology paths in the LED lighting industry – sapphire substrate, silicon carbide substrate and silicon substrate,» said Eric Luo, SFCE's executive director and CEO. «While the first two of these technologies have already been monopolized in the US and Japan, after a decade of research and development, the silicon substrate technology has finally been patented and commercialized by Lattice Power in China. I would like to congratulate Professor Fengyi Jiang, Dr. Qian Sun, Dr. Min Wang and their team at Lattice Power for achieving this

impressive technological breakthrough and winning this award.» Read more Vishay launches metal-core-based cool-white LED power module Semiconductor Today

Vishay Intertechnology Inc of Malvern, PA, USA has launched a new metal-core-based cool-white LED power module featuring 12 high-brightness LEDs with high luminous flux of 4000lm each at 1A. To simplify designs and manufacturing processes, the Vishay Semiconductors VLSL12A03-3Q3T-50A can be combined with off-the-shelf LEDiL quadruple lenses, while its integrated small thermal sensor (NTCS0603E347JHT) and fourfold plug-in connector (87438-0443) eliminate the need for additional soldering. Read more Nikkiso to begin shipping record-power 50mW UVC deep UV LEDs Semiconductor Today

Nikkiso America Inc of San Diego, CA, USA (the US arm of Tokyo-based Nikkiso Co Ltd, which is developing and commercializing deep ultraviolet LEDs) has announced general availability of 50mW deep UV LEDs. The VPS173 series UV LED product range delivers about 1.7 times the power output of the previous generation, with demonstrated operating lifetimes in excess of 10,000 hours at 350mA drive current. Initial 50mW deep UV LED availability will include 285nm components in a surface-mount device (SMD) configuration, with pending releases of products emitting at wavelengths from 265nm to 300nm. «UV LED technology is advancing rapidly, with extraordinary progress reported annually in optical output power, efficiency and cost,» says Nikkiso America's president & CEO Dennis Martin. «Whether the application involves curing, medical, germicidal or analytical instrumentation,

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deep UV LED technology offers compelling advantages over lamp-based solutions and further enables new applications,» he adds. Nikkiso's proprietary aluminium gallium nitride (AlGaN) semiconductor technology was developed by 2014 Nobel Prize winning professors Akasaki and Amano and enables what is claimed to be the world's highest performance and efficiency in the UV-B and UV-C portions of the spectrum. Production facilities are located in Japan's Ishikawa Prefecture and include epitaxy, wafer fab and packaging. Read more

ELECTRONICS

Power electronics MOCVD market growing at 40% CAGR to over $205m in 2019 Semiconductor Today

The global metal-organic chemical vapor phase deposition (MOCVD) market for power electronics is will rise at a striking compound annual growth rate (CAGR) of over 40% to more than $205m in 2019, according to the report 'Global MOCVD Market in Power Electronics 2015-2019' by market research firm Technavio. Read more Going beyond gallium nitride transistor state-of-the-art performance Semiconductor Today

Figure 1: Schematic cross section (upper figures) and transmission electron micrographs (TEMs) of gate region (lower figures) of (a) recessed-gate MISHEMT and (b) p-GaN HEMT.

The imec research center in Belgium claims beyond state-of-the-art performance for a p-type gallium nitride (p-GaN) high-electron-mobility transistor (HEMT) on silicon operating in enhancement-mode (normally-off). The threshold voltage was +2V. Low on-resistance of 7Ω-mm enabled high drive current of 0.4A/mm at 10V drain bias. imec presented its results at the IEEE International Electron Devices Meeting in Washington DC, USA (8 December 2015) in sessions 16.2 and 35.4. imec claims that the p-GaN HEMT outperforms metal-insulator-semiconductor (MISHEMT) counterparts. Read more HELLA, GaN Systems and Kettering University develop 2.6kW/l, 97%-efficient electric vehicle charger Semiconductor Today

Germany-based automotive electronics specialist HELLA, in collaboration with GaN Systems Inc of Ottawa, Ontario, Canada (a fabless developer of gallium nitride-based power switching semiconductors for power conversion and control applications) and charging technology researchers at the Advanced Power Electronics Lab of Kettering University in Flint, MI, USA have developed a Level-2 electric vehicle (EV) charger prototype with efficiencies exceeding 97% at what is claimed to be an unprecedented 2.6kW/l power density. Prior to this, Level-2 EV chargers reached maximum efficiencies of 94%. Using GaN Systems' 60A, 650V GS66516T switches in a two-stage architecture, the Kettering University team - led by Dr Kevin Bai (associate professor of electrical engineering) and known for collaborating with companies to help advance their charging technology - were able to increase the wall-to-battery efficiency to more than 3% greater than that previously obtained. The power density of more than 2.6kW/l is «a significant milestone with important implications for charging electric vehicles, among other charging applications,» states Bai, who characterizes the development as a 'game changer' for the EV charging industry. Read more

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UK's EPSRC Centre for Power Electronics and GaN Systems launch Future Power Challenge Semiconductor Today

GaN Systems Inc of Ottawa, Ontario, Canada, a fabless developer of gallium nitride (GaN)-based power switching semiconductors for power conversion and control applications, together with the Centre for Power Electronics of the UK's Engineering and Physical Sciences Research Council (EPSRC), have launched the Geoff Haynes Future Power Challenge, a new competition open to all UK power electronics postgraduates. The annual award will be worth £2000 for the research paper or poster that makes the strongest contribution to accelerating the use of GaN transistors in future power conversion or control applications. The prize is established to mark the occasion of Geoff Haynes' recent retirement as a founder & vice president of GaN Systems and is in recognition of his contribution to the firm and the formative gallium nitride power industry. Read more Fujitsu develops GaN power amplifier with world's highest output performance for W-Band wireless transmissions i-micronews

Output performance is 1.8 times greater than before, enabling over 30% greater range for high-speed wireless networks. Fujitsu Limited and Fujitsu Laboratories (collectively «Fujitsu») announced the development of a gallium-nitride (GaN)(1) high-electron mobility transistor (HEMT)(2) power amplifier for use in W-band (75-110 GHz) transmissions. This can be used in a high-capacity wireless network with coverage over a radius of several kilometers.

Figure 1: Cross-sectional diagram of the GaN-HEMT device

Figure 4: Performance index of GaN-HEMT power amplifiers

In areas where fiber-optic cable is difficult to lay, to achieve high-speed wireless communications of several gigabits per second, one promising approach is to use high-frequency bands, such as the W band, which uses a wide frequency band. In order to get good long-distance coverage in these frequencies, however, it is necessary to increase the output power of the power amplifier to the scale of watts. Fujitsu succeeded in developing a power amplifier for W-band transmissions using GaN-HEMT technology capable of high output at 100 GHz. Evaluations of the newly developed power amplifier confirmed it to have 1.8 times increased output performance than before, which would translate to an increase of over 30% in transmission range when used in a high-speed wireless network. A portion of this research was conducted as part of a project of the National Institute of Information and Communications Technology (NICT) on "Agile Deployment Capability of Highly Resilient Optical and Radio Seamless Communication Systems." Details of this technology are being presented at Power Amplifiers for Wireless and Radio Applications (PAWR2016), opening January 24 in Austin, Texas. Read more

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Wide Band Gap technologies, an opportunity to increase power devices performance i-micronews

When people think about Wide Band Gap (WBG) materials for power electronics applications, they usually think of GaN or SiC. This is a not a surprise: indeed SiC and GaN are currently the most advanced WBG technologies for power electronics applications. However, there are materials with an even larger band gap which can further increase power device performance. What is the development status of such innovative technologies? Are there already some products available on the market? What is the added-value of such materials? Yole Développement (Yole) proposes today a comprehensive overview of the whole WBG solutions dedicated to the power electronics industry. This survey is entitled SiC, GaN and other WBG materials for power electronics applications. Including a detailed analysis of the most advanced WBG materials, SiC and GaN, Yole’s report also highlights the added-value of disruptive technologies such as Ga2O3, diamond and AlN. Yole’s analysts detail the status of such new solutions and the related technology roadmap. The “More than Moore” market research and strategy consulting company also presents the technical and market challenges facing WBG players. Read more EpiGaN and SunEdison semiconductor enter into a collaboration to serve GaN-on-Si customers globally i-micronews

EpiGaN, the leading European supplier of commercialgrade 6- and 8-inch GaN-on-Silicon epi-wafers for 600-V HEMT (High Electron Mobility Transistor) power semiconductors, and SunEdison Semiconductor, a leading manufacturer of silicon substrates for semiconductor manufacturing, have signed a global representation agreement forEpiGaN's GaN-on-Si epi wafers. Read more

EpiGaN's board gains Imec veteran to advise on expansion of GaN-on-Si epi product portfolio and services Semiconductor Today

EpiGaN nv of Hasselt, near Antwerp, Belgium, which supplies commercial-grade gallium nitride on silicon (GaN-on-Si) epitaxial wafers for the power switching, RF power and sensor markets, says that Lou Hermans has joined its board of directors as an independent member in an advisory role. Hermans will add his broad expertise in founding and growing semiconductor startups to implementing EpiGaN's expansion and its growing portfolio of GaN-on-Si products and services. In 2007, Hermans co-founded CMOSIS NV of Antwerp Belgium, a provider of CMOS image sensors and solutions, where he served as chairman of the board, VP marketing & sales and chief operating officer. Read more Mitsubishi Electric developed of a microwave heating system that uses 500W-output GaN amplifier modules as heat sources. i-micronews

Mitsubishi and partners focus on chemical industry for high-efficiency heating approach. Mitsubishi Electric, Tokyo Institute of Technology, Ryukoku University and Microwave Chemical have announced the joint development of a microwave heating system that uses 500W-output GaN amplifier modules as heat sources. Read more Japanese project develops microwave heating system using GaN amplifier module heaters Semiconductor Today

Mitsubishi Electric Corp, Tokyo Institute of Technology, Ryukoku University and Microwave Chemical Co Ltd have jointly developed a microwave heating system that uses 500W-output gallium nitride (GaN) amplifier modules as heat sources.

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The modules consume 70% less energy than conventional external heating systems that use fossil fuel and improve chemical-reaction productivity three-fold compared with dispersed heating systems. Practical uses will now be developed for high-level energy saving in the chemical industry. Read more Plextek RFI adds GaN power amplifier expert to design team Semiconductor Today

Plextek RF Integration of Cambridge, UK, which designs and develops RFICs, MMICs and microwave/millimeter-wave modules, has strengthened its capabilities with the addition of Robert Smith to its team of design engineers. «We are seeing increasing demand for our design skills from right across the industry, in applications ranging from defence and aerospace through wireless technology and satellite communications to test and measurement,» notes CEO Liam Devlin. Read more Raytheon's GaN-based AESA Patriot air & missile defense radar completes key milestones Semiconductor Today

Raytheon Company of Waltham, MA, USA recently completed a series of company-funded milestones to upgrade the combat-proven Patriot Air and Missile Defense System. The projected upgrade delivers 360° capability, aiming to keep Patriot ahead of increasingly more sophisticated threats, such as aircraft, drones and cruise and ballistic missiles. The Patriot radar main array was enhanced with gallium nitride (GaN)-based active electronically scanned array (AESA) technology. The same Raytheon engineers who completed those milestones are currently constructing a GaN-based AESA, full-size, main panel radar array (on track to

have a full-scale main array prototype operational in early 2016 – just 24 months after the firm began building it). Read more EPC launches development board with 50A, 1MHz capability to reduce size in point-of-load applications Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, has introduced the EPC9059 half-bridge development board for high-current, high-frequency point-of-load (POL) applications using eGaN ICs to reduce power conversion size. The EPC9059 development board has a 30V maximum device voltage with a 50A maximum output current. In this application, two 30V EPC2100 eGaN ICs operate in parallel with a single onboard gate driver to achieve higher output currents. EPC says that GaN devices have superior current-sharing capability compared to silicon MOSFETs, making them more attractive for parallel operation. Read more EPC posts video series on how to design with GaN power devices for power conversion Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, has expanded its video library on GaN technology by adding a nine-part educational video series to provide power system design engineers with technical information and application examples on how to design more efficient power conversion systems using GaN-based transistors and integrated circuits. http://epc-co.com/epc/DesignSupport/TrainingVideos.aspx

Read more

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EPC launches development boards for 200V eGaN FETs operating up to 30MHz Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, has launched high-efficiency GaN-based differential mode development boards that can operate at up to 30MHz, providing an easy-to-use way for power systems designers to evaluate the performance of GaN transistors and get their products into volume production quickly, says the firm. Read more EPC's CEO & co-founder Alex Lidow receives SEMI Award for North America Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, says that at the Industry Strategy Symposium (ISS) banquet of SEMI (industry association Semiconductor Equipment and Materials International) in Half Moon Bay, CA, USA (on 12 January) its CEO & co-founder Dr Alex Lidow was presented with the 2015 SEMI Award for North America (in the area of Process and Technology Integration) for innovation in power device technology, enabling the commercialization of GaN devices with performance and cost advantages over silicon. Read more EPC recruits Yuanzhe Zhang as director, Applications Engineering Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, says that Dr Yuanzhe Zhang has joined its engineering team as director, Applications Engineering. Read more

EPC launches eGaN power transistor enabling higher resolution in augmented reality and autonomous vehicle applications Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, has launched the EPC2040 power transistor, an extremely small, fast-switching GaN power transistor that enables superior resolution, faster response time, and greater accuracy for high-speed end-use applications. Read more Qorvo's quarterly revenue falls 12% after demand pause from largest Mobile Products customer Semiconductor Today

For its fiscal third-quarter 2016 (to 2 January), Qorvo Inc (which provides core technologies and RF solutions for mobile, infrastructure and defense applications) has reported revenue of $620.7m (well below the original guidance of $720-730m), down 12% on $708.3m last quarter and 16% on $742m a year ago for the combined December 2014 quarter revenues of RF Micro Devices Inc of Greensboro, NC and TriQuint Semiconductor Inc of Hillsboro, OR, USA (following the merger of the two firms on 1 January 2015). Nevertheless, in Qorvo's first full year, compared to calendar 2014, revenue grew 12%. Read more

OTHER

Riber's annual revenue falls 23% to €12.8m in 2015 Semiconductor Today

Riber S.A. of Bezons, France, which manufactures molecular beam epitaxy (MBE) systems as well as evaporation sources and effusion cells, has reported a second consecutive year of reduced revenue (€12.8m for 2015, down 23% on 2014's €16.6m), linked primarily to the MBE market's

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significant contraction over the past two years during a cyclical low. The majority of orders were booked in second-half 2015, yielding revenue of €7.1m (€5.1m in Q4 plus €2m in Q3) compared with €5.7m in first-half 2015 (€3m in Q2 plus €2.7m in Q1), as the year was marked by significant fluctuations in MBE system sales. System revenue specifically was €6.1m for 2015, down 35% on €9.3m for 2014. Read more NCSU discovers new phase of boron nitride and new way to create pure c-BN Semiconductor Today

North Carolina State University (NCSU) has discovered a new phase of boron nitride (Q-BN) that has potential applications for both manufacturing tools and electronic displays. The researchers have also developed a new technique for creating cubic boron nitride (c-BN, with a cubic crystalline structure, analogous to diamond) at ambient temperatures and air pressure, which has applications including the development of advanced power grid technologies. Read more

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PATENT APPLICATION

More than 90 new patent applications were published between 2016-01-02 and 2016-02-01.

Patent Applicants Number of

new patent applications

Xiangneng Hualei Optoelectronic Corp. 5

Toyoda Gosei 4

South China University Of Technology 4

Sharp 3

Hexasolution 3

Sumitomo Electric Industries 3

Panasonic 3 Other patent applicants: Aixtron, Alcatel Lucent, Canon Anelva, CEA, China Electronics Technology, Comba Telecom System, Episil Semiconductor Wafer, Furukawa, Hangzhou Silan Azure, HC Semitek, Hebei University Of Technology, Hitachi High Technologies, IBM, Iljin LED, Indian Institute Of Science, Institute Of Semiconductors, Intermolecular, LG Innotek, Lightwave, Lumistal, Nanjing University Of Technology, Nantong Tongfang Semiconductor, NGK Insulators, Nichia, Ningbo University, Raytheon, RayVio, SAMCO, Sanan Optoelectronics, Semiconductor Components Industries, Seoul National University (SNU), Seoul Viosys, Shandong University, Shanghai Aerospace Measurement Control Communication Research Institut, Silan, Soft Epi, Soraa, Southeast University (Nanjing China), Suzhou Institute Of Nano Technology & Nano Bionics (Chinese Academy Of Sciences), Tamura, Toyota Central R&D Labs, Toyota Motor, Transphorm, Tsinghua Tongfang, University Beijing, University Of Shanghai For Science & Technology, Ushio Electric, Wuxi China Resources Huajing Microelectronics, Xidian University …

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New patent applications selected by Knowmade Double heterojunction group III-nitride structures Publ. Nb: US9231064 Patent Applicant: Raytheon (US)

A semiconductor structure having: a Group III-N channel layer, a Group III-N top-barrier polarization-generating layer forming a heterojunction with an upper surface of the channel layer; and a Group III-N back-barrier polarization-generating layer forming a heterojunction with a lower surface of the channel layer. The channel layer has disposed therein a predetermined n-type conductive dopant. Read more

UV light emitting devices and systems and methods for production Publ. Nb: US2016027962 Patent Applicant: RayVio (US)

A method of fabricating an ultraviolet (UV) light emitting device includes receiving a UV transmissive substrate, forming a first UV transmissive layer comprising aluminum nitride upon the UV transmissive substrate using a first deposition technique at a temperature less than about 800 degrees Celsius or greater than about 1200 degrees Celsius, forming a second UV transmissive layer comprising aluminum nitride upon the first UV transmissive layer comprising aluminum nitride using a second deposition technique that is different from the first deposition technique, at a temperature within a range of about 800 degrees Celsius to about 1200 degrees Celsius, forming an n-type layer comprising aluminum gallium nitride layer upon the second UV transmissive layer, forming one or more quantum well structures comprising aluminum gallium nitride upon the n-type layer, and forming a p-type nitride layer upon the one or more quantum well structures. Read more

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Device including a light-emitting diode and a transformer associates Publ. Nb: FR3024010 Patent Applicant: Alcatel Lucent (FR), CEA - Commissariat A L’Energie Atomique Et Aux Energies Alternatives (FR)

Machine translated Abstract

The invention relates to a device of lighting (1), including: - an alternate converter/continuous step-down transformer (3), including: - an interface of entry (11, 12) of alternating voltage, and an interface of exit (13.14); - a light-emitting diode (21) connected between terminals of the interface of exit; - a resistance connected to form a tension divider with the light-emitting diode compared to a tension applied to the interface of entry; - a regulating circuit of tension; - the aforementioned resistance including a first transistor to heterojunction with field effect (301) and the regulating circuit including a second transistor with heterojunction (304) with field effect, the first and second transistors comprising a layer of [GaN], a layer of [AIGaN], and a gas of electrons to the interface between these layers, the light-emitting diode being formed on the aforementioned layer of [AIGaN]. Read more

Forming enhancement mode iii-nitride devices Publ. Nb: WO2016014439 Patent Applicant: Transphorm (US)

A method of fabricating a III-N device includes forming a III-N channel layer on a substrate, a III-N barrier layer on the channel layer, an insulator layer on the barrier layer, and a trench in a first portion of the device. Forming the trench comprises removing the insulator layer and a part of the barrier layer in the first portion of the device, such that a remaining portion of the barrier layer in the first portion of the device has a thickness away from a top surface of the channel layer, the thickness being within a predetermined thickness range, annealing the III-N device in a gas ambient including oxygen at an elevated temperature to oxidize the remaining portion of the barrier layer in the first portion of the device, and removing the oxidized remaining portion of the barrier layer in the first portion of the device. Read more

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GANEX | Newsletter No. 37 - III-N Technology 52

Side-emitting type nitride semiconductor light emitting chip and side-emitting type nitride semiconductor light emitting device having the same Publ. Nb: WO2016006781, KR20160005827 Patent Applicant: Iljin LED (KR)

Disclosed are a side-emitting type nitride semiconductor light-emitting chip, which includes a first and second reflective layers formed on both surfaces thereof, respectively, so as to enable light to be emitted only from the sides thereof, thereby easily realizing white light, and a light-emitting chip having the side-emitting type nitride semiconductor light-emitting chip. Read more Procedure for separating pillared structures Publ. Nb: DE102014109335 Patent Applicant: Aixtron (GE)

Machine translated Abstract

The Invention concerns a Procedure for Separating pillared Structures (7) from a Iii V material, an in particular [GaN] or a [AlGaN], whereby on the Surface of a Substrate (1) or on the Surface of a [Bufferschicht] separated on it

not-closed, in particular [inselformige] first Open Spaces (3) exhibiting first Masking Layer (2) is separated, whereby on the first Open Spaces (3) the Masking Layer (2) completely covering Germ Layer (4) is separated, which exhibits a Separating of the pillared Structures a friendly Surface, whereby on the Germ Layer (4) not-closed, [inselformige] second Open Spaces (6) surrounding second Masking Layer is separated, which exhibits a Separating of the pillared Structures a hostile Surface, whereby the column-like Structures (7) in the second Open Spaces (6) to be separated. The Moreover One the Invention concerns an opto-electronic Element with one on a SI-substrate separated first Open Spaces (3) exhibiting first Masking Layer (2) from [SiN]. In Addition the Invention a monolithic Circuit developed on a SI-substrate concerns also one or more MOS components. Semiconductor device Publ. Nb: WO2016002473 Patent Applicant: Sharp (JP)

The purpose of the present invention is to achieve improvements in yields during fabrication of GaN-HEMTs. The present invention is provided with an external connection terminal (126 (D)) performing the role of a drain for a semiconductor device (150) and two or more GaN-HEMTs (104). The drain

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GANEX | Newsletter No. 37 - III-N Technology 53

pad ((D)) of each GaN-HEMT (104) is connected to the external connection terminal (126 (D)). Read more Three-color light source Publ. Nb: WO2016002267, JP2016015415 Patent Applicant: Sumitomo Electric Industries (JP)

A three-color light source (1), which outputs red, green, and blue laser light as combined waves, is provided with red LD (11), green LD (12), blue LD (13), a first collimating lens (61), a second collimating lens (62), a third collimating lens (63), a first wavelength filter (81), a second wavelength filter (82), a carrier (30) whereon LDs (11 - 13), the collimating lenses (61 - 63), and the wavelength filters (81, 82) are mounted, and TEC (40) whereon the carrier (30) is mounted. The red LD (11) is constituted of a GaAs based material, and the green LD (12) and blue LD (13) are constituted of a GaN based material. Read more

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