iii-nitride quantum materials and nano-structures for new ... · • blue led 1997 (nakamura &...
TRANSCRIPT
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Zhe Chuan Feng, White LED, 2007 July
III-Nitride Quantum Materials and Nano-structures for New
Generation Light Emitting Devices
Zhe Chuan Feng (馮哲川)Professor, National Taiwan University
Graduate Institute of Electro-Optical Engineering & Department of Electrical Engineering, Taipei, Taiwan, ROC
{國立台灣大學光電工程學研究所暨電機工程學系}Tel: +886-2-3366-3543; E-mail: [email protected]
Web: http://eoe.ntu.edu.tw/; http://ee.ntu.edu.tw/
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Zhe Chuan Feng, White LED, 2007 July
Blue and White Light Emitting Devices
- New Era of Solid-State Lighting
Part-I :
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Zhe Chuan Feng, White LED, 2007 July
• General– Historical Developments in Lighting for human being -
• News & information from Blue 2005• Semiconductor LED & Lighting in Taiwan• R&D from LumiLEDs• Basis of LED and Technology
– Semiconductor LED, MQW LEDs, Resonance Cavity LEDs– Phosphor Technology - Organic LED
• Fabrication Technology - Semiconductor LED – MOCVD growth of III-Ns, Characterization, Processing– LED Fabrication Technology
• Marketing and further Development for LEDs– LED advantages in comparison with others– More applications & future development
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Zhe Chuan Feng, White LED, 2007 July
GENERAL GENERAL -- Lighting HistoryLighting History
• Burning wood ~50,000 years ago• Gas Lighting ~1772• Electric Lighting ~1876• Incandescent Filament Lamp ~1879 (Swan & Edison) • First LED 1907 SiC (H.J. Round)• Fluorescent Lamps 1938• Red LED 1962 (Holonyak & Bevacqua) - AlInGaP 1990’s• Blue LED 1997 (Nakamura & Fasol)
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Zhe Chuan Feng, White LED, 2007 July
Revolutions in Solid State Electronics andRevolutions in Solid State Electronics and OptoelectronicsOptoelectronics
1940-1950
1980-2000
1990-2020+
Vacuum tubes Transistors
CRTTV
Flat PanelTV /
Displays
Solid State Lighting
Light bulbs
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Zhe Chuan Feng, White LED, 2007 July
0.01
0.1
1
10
400 450 500 550 600 650 700Wavelength (nm)
InGaN AlInGaP
AlGaAs
GaAsP GaAsPGaP:N
SiC
Color: Ultra-violet Blue Green Yellow Orange Red Infra-Red
Better
Worse
Luminous
IntensityLow PerformanceCommodity LEDs
LEDS LEDS –– Material Systems, Colors and BrightnessMaterial Systems, Colors and Brightness
LightLight EmittingEmitting DiodesDiodes ((LEDsLEDs))
Materials – High Birght & White LED - OLED
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Zhe Chuan Feng, White LED, 2007 July
Applications ofApplications of LEDsLEDs
After Compound Semiconductor Magzine
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Zhe Chuan Feng, White LED, 2007 July
Human EyeHuman Eye
Based on empirical data of human
vision
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Zhe Chuan Feng, White LED, 2007 July
Semiconductor LEDand
Semiconductor Lighting in Taiwan
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Zhe Chuan Feng, White LED, 2007 July
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Zhe Chuan Feng, White LED, 2007 July
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Zhe Chuan Feng, White LED, 2007 July
People interested in LED show
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Zhe Chuan Feng, White LED, 2007 July
Some technical issues in Semiconductor LED & Lighting
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Zhe Chuan Feng, White LED, 2007 July
Lattice Constant Lattice Constant vsvsBandgapBandgap
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Zhe Chuan Feng, White LED, 2007 July
InGaNInGaN//GaNGaN MQW LED on MQW LED on sapphiresapphire
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Zhe Chuan Feng, White LED, 2007 July
Resonant Cavity Nitride-LED
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Zhe Chuan Feng, White LED, 2007 July
AlGaInP LEDsAlGaInP LEDs
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Zhe Chuan Feng, White LED, 2007 July
Blue/UV LED Pump Source for PhosphorsBlue/UV LED Pump Source for Phosphors
• GaN based LEDsgenerate UV light
• UV light is absorbed by appropriate phosphor(s)
• Phosphor converts UV radiation to light of desired colors
• White light generation by phosphor mixing
Contacts
(InAlGa)N
n-GaNUV/Blue
Phosphor Layer
VISIBLE EMISSION
p-GaN
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Zhe Chuan Feng, White LED, 2007 July
LED Strings, Drive Circuits, AssemblyLED Strings, Drive Circuits, Assembly
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Zhe Chuan Feng, White LED, 2007 July
• Epitaxy of materials• Characterization of epitaxy
structural materials
• Processing• Packaging• Device Tests
LED Fabrication TechnologyLED Fabrication Technology
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Zhe Chuan Feng, White LED, 2007 July
Crystal Growth Techniques
•Liquid Phase Epitaxy (LPE) (no GaN or InGaAlP)In LEDs - used mostly for IR and AlGaAs red LEDs
•Vapor Phase Epitaxy (VPE) (hydride VPE or HVPE)
In LEDs - used mostly for low brightness GaP and GaAsP LEDsAlso used by HP for GaP window growth on HB AlInGaP LEDsStarting to be used in GaN for “substrate” growth
•Metal Organic Chemical Vapor Deposition (MOCVD)(OMVPE, MOVPE: Metal Organic Vapor Phase Epitaxy) - Most widely used technique for High Brightness LEDs
•Molecular Beam Epitaxy (MBE)
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Zhe Chuan Feng, White LED, 2007 July
MOCVD System
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Zhe Chuan Feng, White LED, 2007 July
Flow Patterns During MOCVD GrowthFlow Patterns During MOCVD Growth
Computer Generated Flow Patterns in Rotating Disc System
Smoke Flow Patternsin Rotating Disc System
Data Courtesy of Sandia National Laboratories
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Zhe Chuan Feng, White LED, 2007 July
LED processingLED processing
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Zhe Chuan Feng, White LED, 2007 July
General Blue LED Process General Blue LED Process FlowFlow
N-GaNIn-GaNP-GaN
PR Strip
N-GaNIn-GaNP-GaNNi/Au
Metal Lift-off
N-GaN
In-GaNP-GaNNi/Au
Al/Ti/Pt/Au
Ni/Au
Metal Lift-off
N-GaN
In-GaNP-GaNNi/Au
Al/Ti/Pt/Au
Resist Resist
Photo Level 4N-GaN
In-GaNP-GaNNi/Au
Al/Ti/Pt/Au
Resist Resist
Ni/Au
Evaporation
N-GaNIn-GaN
ResistP-GaN
Photo Level 1
Oxidation
Contact Alloy
Native Oxide Removal
N-GaN
In-GaNP-GaNNi/Au
Al/Ti/Pt/Au
Metal Lift-off
ContactAlloy
P-metal Alloy
Photo Level 2
N-GaN
In-GaNP-GaNNi/Au
Resist
Mesa Etch :
Transparent Contact:
N-layer Metal:
P-bonding Pad:
N-GaN
In-GaNP-GaNNi/Au
Resist
Evaporation
Al/Ti/Pt/Au
N-GaNIn-GaN
ResistP-GaN
RIE
Resist
Photo Level 3
N-GaNIn-GaNP-GaN
Resist Resist
N-GaNIn-GaNP-GaN
Resist Resist
Evaporation
Ni/Au
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Zhe Chuan Feng, White LED, 2007 July
Standard GaN LED Fab ProcessesStandardStandard GaNGaN LEDLED FabFab ProcessesProcesses
p GaN
SUBSTRATE
Active Region
n GaN
Semi-transparent contact formation
p GaN
SUBSTRATE
Active Region
n GaN
Semi-transparent contact
Mesa and isolation etch
p GaN
SUBSTRATE
Active Region
n GaN
Passivation formation
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Zhe Chuan Feng, White LED, 2007 July
p GaN
SAPPHIRE SUBSTRATE
Active Region
n GaN
SiO2Semi-Transparent
Contact
P-pad
N-padGaN:Mg (p-doping)
(Ga,In)N Active Layer
Nucleation Layer
Contract geometry
P-type contact
A Standard GaN Blue LED Chip
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Zhe Chuan Feng, White LED, 2007 July
White LED Technology: Binary complementaryWhite LED Technology: Binary complementary
• Wavelength– Blue GaN 470nm– YAG 572nm
400 500 600 7000.0
0.5
1.0
1.5
T=4500 KRa=90K=330 lm/W
Wavelength (nm)
Inte
nsity
(arb
. uni
ts)
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Zhe Chuan Feng, White LED, 2007 July
New Packaging (New Packaging (LuxeonLuxeon//LumiledsLumileds))
Emitter
Star
Line
Ring
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Zhe Chuan Feng, White LED, 2007 July
LED PackagingLED Packaging
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Zhe Chuan Feng, White LED, 2007 July
Imperative forLighting
Applications
High-Power LED
LED Output Power Improvement
High Internal Efficiency Material
Efficient Light ExtractionChip
High Operating Current
High Current Density
Large Chip
Theoretical limit is 30 Lm at 20mA!
1000 Lm
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Zhe Chuan Feng, White LED, 2007 July
Organic LightOrganic Light--Emitting Diode (OLED)Emitting Diode (OLED)
(from IBM Almaden)
Organic light-emitting devices (OLEDs) operate on the principle of converting electrical energy into light, a phenomenon known as electroluminescence. In its simplest form, an OLED consists of a layer of this luminescent material sandwiched between two electrodes. When an electric current is passed between the electrodes, through the organic layer, light is emitted with a color that depends on the particular material used.
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Zhe Chuan Feng, White LED, 2007 July
OLED: Physics and FabricationOLED: Physics and Fabrication
(from Univ. of Arizona)
An electric field is applied to the device. On the ITO layer, holes are induced into the hole-conducting polymer layer At the same time, electrons from the cathode are injected in the electron-conducting layer.
OLEDs: on a transparent substrate, the first electrode deposited (~100nm), one or more organic layers coated by either thermal evaporation or spin coating of polymers (~100 nm), metal cathode (such as magnesium-silver alloy, lithium- aluminum or calcium) evaporated on top (~100 nm).
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Zhe Chuan Feng, White LED, 2007 July
LED Markets, Advantages & FuturesLED Markets, Advantages & Futures
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Zhe Chuan Feng, White LED, 2007 July
LED Efficiency LED Efficiency SummarySummary
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Zhe Chuan Feng, White LED, 2007 July
More More Fascinating Fascinating
Applications of Applications of Semiconductor Semiconductor & White& White LEDsLEDs
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Zhe Chuan Feng, White LED, 2007 July
High-Brightness LEDs – Some New Applications
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Zhe Chuan Feng, White LED, 2007 July
High-Brightness LEDs – Some New Applications
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Zhe Chuan Feng, White LED, 2007 July
The World’s First Operation under only LED Lighting
Junichi Shimada Department of Thoracic Surgery, Kyoto Prefectural University of Medicine and Division of Surgery, Kyoto Prefectural Yosanoumi Hospital, Japan
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Zhe Chuan Feng, White LED, 2007 July
LEDs in Cars - 2
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Zhe Chuan Feng, White LED, 2007 July
LEDs in Car - 3
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Zhe Chuan Feng, White LED, 2007 July
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Zhe Chuan Feng, White LED, 2007 July
LEDs in Cars - 1
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Zhe Chuan Feng, White LED, 2007 July
White & Blue Light Devices will
be quickly and widely developed
and applied in Science,
Technology and Human Life
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Zhe Chuan Feng, White LED, 2007 July
Part-II
InGaN/GaN Multiple Quantum Well Light Emitting Diodes:
Basic Mechanisms of
Energy-Efficient Luminescence
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Zhe Chuan Feng, White LED, 2007 July
2.5 3.0 3.5
M O C V D
Q W 8a
PL
Inte
nsity
(a.u
.)
Energy (eV)
Tem p. : 9K 16K 20K 30K 40K 50K 70K 90K 110K 140K 170K 200K 250K 300K
14.09m W
InGaN/GaN 8QW s(W) 1.2nm (B) 3nm 8-QWs x(In)=17.8%
Left:Emissions- QW
Right:Emissions- GaN barriers
InGaN/GaN 8QWs: Temperature dependent PL
Temperature dependent PL
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Zhe Chuan Feng, White LED, 2007 July
0 50 100 150 200 250 3002.6
2.7
3.4
3.5
Peak
Ene
rgy
(eV)
Temperature (K)
InGaN/GaN 8QWsQW8a
GaN band
MQW emission
0 20 40 60 80 100
0.3
0.4
0.5
0.6
0.7
0.80.9
11.1
InGaN/GaN 8QWs
Internal quantum efficiency (IQE)at 300K = 34.8%
Inte
grat
ed P
L In
tens
ity (a
.u.)
1000 / T (K-1)
PL peak position versus T (9–300 K)
η(Internal Quantum Efficiency):The time integrated photoluminescence intensity at room temperature normalized to a low temperature (9K) value
(W) 1.2nm / (B) 3nm x 8 x(In) : 17.8%Varshni Eq. for Eg(GaN) – T:E(T)=E(0)-αT2/(β+T)E(0) =2.7015 eV
α = 0.368 meV/K, β = 618 K
Anomalous T-behavior of MQW PL peak is attributed to band-tail states due to inhomogeneities in the InGaN-based material.
InGaN/GaN 8QWs: Peak position & Arrhenius plot
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Zhe Chuan Feng, White LED, 2007 July
2.0 2.5 3.0 3.50.0
0.5
1.0 InGaN/GaN 8QWs
PL
PL
Inte
nsity
(a.u
.)
Energy (eV)
PLE
216meV
QW 8a
Comparison of RT PL and PLE spectra from a MOCVD-grown InGaN-GaNMQW (8-QWs) sample – Quantum confined Stark effect (QCSE).
InGaN/GaN 8QWs: PL & PLE spectra
Photoluminescence excitation (PLE)
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Zhe Chuan Feng, White LED, 2007 July
TRPL of InGaN/GaN QWs
TRPL Dependences on Excitation power variation Detection λ
M. Pophristic, F.H. Long, C.A. Tran, R.F. Karlicek, Z.C. Feng & I. Ferguson, “Time-resolved spectroscopy of InxGa1-xN multiple quantum wells at room temperature”, Appl. Phys. Lett. 73, 815-817 (1998).
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Zhe Chuan Feng, White LED, 2007 July
InGaN MQW LEDRE26461 nm 10kt1 = 23.02 ns
fitting begins at 1ns(a)
0 40 80 120 160
fitting begins at 1ns
461 nm 240Kt1 = 3.81 ns
time (ns)
0 50 100 150 200 250 300
InGaN MQW LEDRE26T
ime
Con
stan
t (ns
)
Temperature (K)
• T-dependence of lifetime (10-300 K), measured at PL peak -462 nm.
• Typical TRPL data and fittings at two temperatures of 10 and 240 K.• A single-exponential fit - determine the lifetime.
TRPL on newly MOCVDTRPL on newly MOCVD--growngrown InGaNInGaN//GaN MQWsGaN MQWs
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Zhe Chuan Feng, White LED, 2007 July
2.0 2.5 3.0
fitInGaN MQW LEDRE26
PL
lifet
ime
(ns)
Photon Energy (eV)
PL
inte
nsity
(a.u
.)
2
3
4
5
6
0 10 20 30 40
----- laser----- fit
InGaN MQW LEDRE26440 nm (2.817 eV)t1 = 2.51 ns
PL
inte
nsity
(a.u
.)
(a)
time (ns)
• TRPL data and fittings atλ=440 nm. Fittingbegins at about 1.5 ns in order to avoid the laser response.
• The RT TRPL was measured from 436nm to 492nm, with 15 points. The t PL values increase with decreasing photon energy.
• This is characteristic of the localized system. The depth of localization can be evaluated by assuming the exponential distribution of the density of tail states and by fitting the photon energy dependence of the t PL values using the equation:
(A pulsed laser 374 nm)
TRPL ofTRPL of InGaNInGaN//GaN MQWsGaN MQWs: dependence on photon energy: dependence on photon energy
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Zhe Chuan Feng, White LED, 2007 July
TRPLTRPL
0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.00.0
200.0
400.0
600.0
800.0
1.0k
1.2k
He-Cd laser: 372.5nm
InGaN MQW25-re35TRPL: 446nmSlit: 0.5mmTime: 60s
Time(ns)
TRP
L In
tens
ity(a
.u.)
0
100
200
300
400
500
600
700
Laser TRP
L Intensity(a.u.)
0
exp1)(
EEE
Eme
radPL −
+=
ττ
2.0 2.5 3.0
535
540
545
InGaN MQW25-re35PLSlit: 0.5mmTime: 0.1s
Energy(eV)
TRP
L In
tens
ity
fit
4
6Data: re35f4d1_CModel: user2 Equation: y=p1/(1+exp((x-p2)/p3)) Weighting:y No weighting Chi^2/DoF = 0.00091R^2 = 0.9984 p1 6.4214 ? .03199p2 3.05437 ? .00317p3 0.12909 ? .00445
DecayTim
e(ns)
RE35τrad =6.42 nsEme =3.05 eVE0 =129 meV
RN37τrad =5.92 nsEme =2.94 eVE0 =104 meV
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Zhe Chuan Feng, White LED, 2007 July
InGaNInGaN//GaNGaN 55--QWsQWs: TEM : TEM bright field imagebright field image & & HighHigh--angle annular dark fieldangle annular dark field (HAADF) (HAADF) imageimage
TEM bright field image from a MOCVD InGaN-GaN MQW LED on sapphire. Structural features of five QWs are clearly seen. The widths of the well and barrier are determined to be 4 nm and 40 nm, respectively. The TEM image shows no threading dislocation at this area, but some strain field around the well, which sometimes may induce V-shape defects and high density of stacking faults.
High resolution transmission electron microscopy
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Zhe Chuan Feng, White LED, 2007 July
InGaNInGaN//GaNGaN 55--QWsQWs: TEM : TEM bright field imagebright field image & & HighHigh--angle annular dark fieldangle annular dark field (HAADF) (HAADF) imageimage
100 nm
HAADF Detector
HAADF STEM contrast is mainly due to thermal diffuse scattering, whose intensity is almost proportional to the square of atomic number. Five bright stripes parallel to the basal plane are InGaN layers and dark ones are GaN layers.
High resolution transmission electron microscopy
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Zhe Chuan Feng, White LED, 2007 July
VV--defects & defects & HAADF STEM HAADF STEM images of theimages of the InGaNInGaN//GaNGaN MQWMQW
(G978)
Threading dislocation originating from GaN/sapphire interface to disrupt the InGaN/GaN MQW, and to initiate the V-defect, which have inverted the hexagonal pyramid-shaped {10-10}side walls.
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Zhe Chuan Feng, White LED, 2007 July (G978)
(b)(a) QW1
Digital Analysis of Lattice image techniqueDigital Analysis of Lattice image technique-- showing QDshowing QD--like structureslike structures
The color-coded map of the local In concentration in anInGaN/GaN QW structure, which contains 5 InGaN layers. (a) is QW1 just next to the capping layer and (e) is QW5 at the bottom
of the active layer.
(e) QW5
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Zhe Chuan Feng, White LED, 2007 July (G978)
HRHR--TEM images from a greenTEM images from a green InGaNInGaN MQW LEDMQW LED
HRTEM images from a green InGaN MQW LED (scale: 20-nm & 2-nm). The In-clustering is seen clearly. These nano-structural or QDs features are closely correlated with results from HRXRD, PL/PLE.
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Zhe Chuan Feng, White LED, 2007 July
Fig. HRTEM images from an InGaN-GaN MQW LED (scale: 50-nm)
HRHR--TEM images from a blueTEM images from a blue InGaNInGaN MQW LEDMQW LED
Fig. HRTEM image from an InGaNMQW LED (scale: 2-nm).
HRTEM from another LED on a QW area, with the In-clustering seen clearly. These nano-structural or QDs features are closely correlated with results from HRXRD, PL/PLE
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Zhe Chuan Feng, White LED, 2007 July
Figure 3 exhibits a HRTEM from another LED on a QW area, with the In-clustering seen clearly. These nano-structural or QDsfeatures are closely correlated with results from HRXRD, PL/PLE
Fig. 3. HRTEM image from an InGaNMQW LED (scale: 2-nm).
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Zhe Chuan Feng, White LED, 2007 July
MonolayerMonolayer fluctuations influctuations in InGaN QWsInGaN QWs
From Humphries et al.
Upper interface(rough)
lower interface(abrupt)
InGaN QWs are not atomically flat
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Zhe Chuan Feng, White LED, 2007 July
InGaN-GaN MQW: HR-XRD & Simulation
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Zhe Chuan Feng, White LED, 2007 July
32 .5 33 .0 33 .5 34 .0 34 .5 35 .0 35 .5
1 0 0
1 0 0 0
1 0 0 0 0
1 0 0 0 0 0
1 0 0 0 0 0 0
34 .3 34 .4 34 .5 34 .6
+ 6+ 5
+ 4
+ 3
+ 2
+ 1
-10 -9-8 -7
-6 -5 -4-3 -2
-1
0
G aN (0002 )
M O C V D
InG aN -G aN M Q W LE D
HR
XR
D In
tens
ity (C
ount
s/se
c)
2 θ (o)
5 -w e lls
G 436
+ 1-1
n= 0
G a N (0 0 0 2 )
InGaN-GaN MQW: excellent characteristic HR-XRD
• GaN peak is very sharp and all satellite bands, which are narrow, up to 10-thorder are obtained. • More fine structures are seen between satellite peaks, indicating the excellent layer crystalline perfection and sharp interfaces between all multiple layers.• Such a nice XRD pattern is reported for the first time in the literature.
(G978)
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Zhe Chuan Feng, White LED, 2007 July
• The computer simulation leads to the precise determination of layer parameters of the thickness and composition
• GaN peak is very sharp and all satellite bands, which are narrow, with high orders obtained.
• Fine structure seen between satellite peaks, indicate the excellent layer crystalline perfection and sharp interfaces between all multiple layers.
InGaN-GaN MQW: HR-XRD Simulation Results
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Zhe Chuan Feng, White LED, 2007 July
Al0.15Ga0.85N/GaN on Al2O3
RSM of (1 0 1) reflection
-0.1
0
0.1
0.2
-0.2-0.1 0 0.20.1 0.3
GaNAlGa
N
0-0.1 0.1
0
-0.1
0.1
GaNAlGaN
HR-XRD Reciprocal Spatial Mapping on AlGaN/GaN
RSM of (004) reflection
AlGaN
5950
5900
6000
2750 2800 2850
Qx*10000
Qy*
1000
0GaN
AlGaN
5950
5900
6000
2750 2800 2850
Qx*10000
Qy*
1000
0GaN
RSM of (1 0 4) asymmetric reflection
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Zhe Chuan Feng, White LED, 2007 July
Raman scattering of a MOCVD undoped GaN/sapphire, (a) normal incidence and (b) cross-section incidence,. (c) and (d) expansions in 500-600 and 700-800 cm-1.
100 200 300 400 500 600 700 800 900 1000
(b) cross-section incidence
(a) normal incidence
sapphire
5145 ? 300 K
MOCVD, GN-d
GaN/sapphire
A1(TO)E1(TO)
E1(LO)
A1(LO)
E2
E2
E2
INTE
NS
ITY
(a.
u.)
RAMAN SHIFT (cm-1)
500 550 600
(c)
A1(TO)
E1(TO)
E2
E2
700 750 800
(d)
RAMAN SHIFT (cm-1)
E1(LO)
A1(LO)
Raman Scattering on Strains-QCSE
200 400 600 800
GaN:
GaN:
x 1
x 1
x 0.03
x 0.03
x 0.3
(h)
(g)
(f)
(e)
(d)
(c)
(b)
(a)
E2
E2
A1(TO)
E1(TO)
E1(LO)
sapphire
sapphire
sufa
cesu
bstra
te
5145 �300 K MOCVD, gn-D
GaN/sapphire
RAMAN SHIFT (cm -1)
700 720 740 760 780 800
x 1
x 1
x 1
x 1
x 0.5
x 0.03
x 0.02
x 0.02
x 0.02(i)
(h)
(g)
(f)
(e)
(d)
(c)
(b)
cross-section incidence
normal incidence
subs
trate
sufa
ce
(a)
E1(LO)
A1(LO)
5145 ? 300 KMOCVD, N71GaN/sapphire
RAMAN SHIFT (cm-1)
Comparative m-Raman spectra of MOCVD-grownGaN/sapphire, with the laser incidence scanning over the film cross-section. The variation of Raman frequency of E1(LO) indicates the strain variation in the film vertical direction.
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Zhe Chuan Feng, White LED, 2007 July
Raman line shape analysis on E2 & A1(LO) modes
Raman high E2 mode and theoretical fit for GaN/sapphire.
540 550 560 570 580 590 600
E2
567.9 cm-1
n-GaN/Sapphire MOCVD
Theoretical Experimental
Raman Shift (cm-1)
Ram
an In
tens
ity (a
.u.)
[ ] 2023221
0 )2/()()
4exp()(
Γ+−−
∫ qqdLqI
ωωαω
21
22 )]}cos(1[{)( qBAAq πω −−+=
700 720 740 760 780 800
5145 �300 K
sapphire EgA1(LO)
n-GaN/sapphire
Inte
nsity
Raman Shift (cm-1)
Experimental Fitted/separated Overall Fitted
Raman determination of carrier concentration:
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Zhe Chuan Feng, White LED, 2007 July
ConclusionConclusion
• InGaN/GaN multiple quantum well light emitting diode (LED) structures are attractive and promising for the next generation high efficiency solid state lighting.
• Basic scientific research needed to fully understand the luminescence origins in this materials.
• Materials growth must be closely coupled to advanced characterization techniques to elucidate physical mechanism
• Experienced research team has been assembled which will guarantee the success of the proposed study
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Zhe Chuan Feng, White LED, 2007 July
Z C Z C FengFeng’’ssbooks,books,
published published in in
19921992--9393--94 :94 :In editing: > 2003:
2006:2004:
GENERAL - Lighting HistoryRevolutions in Solid State Electronics and OptoelectronicsApplications of LEDsHuman EyeInGaN/GaN MQW LED on sapphireAlGaInP LEDsBlue/UV LED Pump Source for PhosphorsLED processingGeneral Blue LED Process FlowStandard GaN LED Fab ProcessesNew Packaging (Luxeon/Lumileds)LED PackagingOrganic Light-Emitting Diode (OLED) OLED: Physics and Fabrication LED Markets, Advantages & FuturesLED Efficiency SummaryTRPL on newly MOCVD-grown InGaN/GaN MQWsTRPL of InGaN/GaN MQWs: dependence on photon energyTRPLDigital Analysis of Lattice image technique �- showing QD-like structuresHR-TEM images from a green InGaN MQW LEDMonolayer fluctuations in InGaN QWsConclusionZ C Feng’s� books,�published in �1992-93-94 :