optoelectronics & photonics

DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution

Air Force Research Laboratory

Integrity Service Excellence


Optoelectronics &

Photonics

Gernot S. Pomrenke, PhD

Program Manager

AFOSR/RTD


MARCH 2014

DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 2 DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution

2014 AFOSR SPRING REVIEW

BRIEF DESCRIPTION OF PORTFOLIO (3001C): Explore light-matter interactions at the subwavelength- and nano-scale between

metals, semiconductors, & insulators.

Explore optoelectronic information processing, integrated photonics, and

associated optical & photonic device components for air and space platforms to

transform AF capabilities in computing, communications, storage, sensing and

surveillance … with focus on nanotechnology approaches. Explore chip-scale

optical networks, signal processing, and novel-sensing .

LIST SUB-AREAS IN PORTFOLIO: - Nanophotonics & Plasmonics: Plasmonics, Photonic Crystals, Metamaterials,

Nano-materials & 2D materials, Opto-mechanics, & Novel Sensing

- Integrated Photonics & Silicon Photonics: Optical Components, Silicon

Photonics, Hybrid Photonics

- Reconfigurable Photonics and Electronics

- Nanofabrication for Photonics: (3-D Assembly, Print, Model & Simulation Tools)

- Quantum Computing w/ Optical Methods (NV diamond, Q-dots in PCs, etc)

- Terahertz Sources & Detectors Exploring light/matter physics, materials, structures, devices, architectures, integration & processing


Focus & Scientific Challenges

--Explore light-matter interactions at the

subwavelength- and nano-scale between

metals, semiconductors, & insulators

--Radiative lifetimes and gain dynamics

--E&M fields & strong nonlinearities

--Efficiently convert optical radiation into

localized energy, and vice versa.

--Enhancing local photo-physical

processes

--Integrating plasmonics with

nanostructured semiconductor devices

(enhance radiative recombination,

generation processes, & understand

loss)

--Growth/fab and placement of nanowires,

quantum dots, 2D materials

--Fundamental building block of info-

processing in the post-CMOS era

--Si Laser & Photonics Simulation Tools

SCIENTIFIC CHALLENGES

--Adding the power and speed of light

waves to traditional electronics could

achieve system performance

inconceivable by electronic means alone.

--By confining light to sub-micron

dimensions, optical nonlinearities can be

enhanced by many orders of magnitude

over free space:

--New class of optical nanostructures –

'photonic bandgap materials' -- that guide

and store light in ways similar to the

processing of electrons in

semiconductors, at fraction of the

wavelength in free space;

--Quantum behavior of light in optical

nanostructures to study information

processing at the fundamental level

FOCUS


PHOTONICS - MOTIVATION

• Significant advances in Photonics & Optoelectronics over the past 15 years and

strong drive for continued growth & innovation

• Robust international commercial markets for Photonics and world-wide R&D for

creating new capabilities:

– US focus to maintain a significant share of Long-Haul (telecom) and Data-Center) (inter-

machine ) interconnect applications

– US continues research lead in intra-machine (Supercomputer) interconnects,

– Existing and planned European Framework and East Asia Programs are strong and

China is moving to close the gap

– Past national initiatives and renewed interest in the USA (NPI)

– Innovations at the component level suggest expanding potential for applications in

embedded supercomputing, quantum computing and all-optical signal processing

• Photonics appears to also offer significant advantages for RF and avionic

systems

• SOI silicon is emerging as a single platform that can provide all optical functions

except laser (3 decades after Si:Er results by Ennen & Pomrenke, APL 43 (10) 15 Nov 83 p.943)

• Opportunities from CMOS electronics - successful scaling of photonics will enable

devices & circuits that offer lower power operation, higher speed, new functionalities,

denser integration


Portfolio Decision

Mission Need:

Advanced Components for EW

ACE Report

ASD(R&E), formerly Mr

Lemnios

AFRL, AF, DOD interactions

Other agencies

Principle Investigators

Reviewer / Evaluator

National & International Colleagues

Economic & DoD System drivers

Workshop Involvement

Workshop – Conference Planning

Review Meetings – AFOSR & other

agencies

Example workshops: Microphotonics –

Boston, NATO – Plasmonics,

Trieste Nanophotonics, Purdue Nanophotonics

Optics Report

National Academies:

Optics and Photonics: Essential

Technologies for Our Nation

ISBN 978-0-309-26377-1

Trends:

Tre

nd

s T

ren

ds


1-Medium term integrated photonics (12 + years):

OpSIS – toward complex systems – Hochberg U DE

Reconfigurable Optical Directed-Logic Circuits – Xu Rice U

Integrated Optoelectronic Networks for Application-Driven

Multicore Computing – Pasricha CSU

New silicon photonics materials: SiGeSn – Kolodzey U DE,

Kouvetakis ASU, Claflin AFRL/RY

Hetero and Monolithic Integration-integration, nano lasers

[III-V & Si] – Huffaker UCLA & Ning ASU

2-Long term integrated photonics (25 + years):

Electrically Pumped Plasmonic Nano-Laser – Zhang UC Berkeley

Hybrid Nanophotonics – Brongersma Stanford U Cavity-Free, Matrix-Addressable Quantum Dot Architecture for On-Chip Optical Switching – Zia Brown U

OUTLINE Integrated Photonics & Nanophotonics

Subareas: Integrated Photonics & Silicon Photonics;

Nanophotonics & Plasmonics

Silicon Photonics

Hybrid Si & III-V

Nano-sized, nano-

structured photonics

Plasmonics Photonics

Q-dot & Q-bit

Photonics

Quantum

Metaphotonics

Now

Future


60

Years

Why did silicon win for electronics?

It was the best platform for integrated systems!

An

opportunity

to support

shared

fabrication

for silicon

photonics

Optoelectronic Systems Integration in Silicon

Prof Michael Hochberg, Univ of Delaware, OpSIS Foundry

opsisfoundry.org/

http

://n

an

op

ho

ton

ics.e

ce

.ud

el.ed

u/a

bo

ut_

the

_la

b.h

tml


OpSIS - Scaling toward complex systems

• We’re seeing a Moore’s Law-like growth in

system complexity

• Doubling time is around a year

• Filling a reticle with photonic devices of

~500 square microns gets us to ~1.7M

devices


OpSIS Institute at UD An opportunity to support shared fabrication for silicon photonics

OpSIS Objective:

•Make integrated photonic fabrication flows easily and cheaply accessible to the research and development community through MPW shared-shuttle processes

•Drive process and tool development and standardization

•Provide educational resources and support to the community

•Develop an ecosystem of service and equipment providers to help move the silicon photonics community forward

~150 users around the world

Half corporate, half academic

0

50

100

150

2011 2012 2013 2014(est)

pre-run 001 002,3,4 005,6,7,8

Active OpSIS Users


OpSIS Research Activities

• Development of design tools & design elements

• Demonstrations of complex systems

• Development of methodology & measurement tools/techniques

• Design automation


Recent results in the OpSIS platform

• Working on run 4 now.

• Runs 1, 2 delivered to ~70 users

• 50 Gbit/second platform – modulators, detectors, low-loss waveguides

• High-efficiency waveguide-coupled photodiodes at 1.2 A/W (not yet published)

• World-record low-loss silicon modulators at 30 GHz (MZI) and 45 GHz (ring)

• Ultra-low loss passives library – crossings, couplers, junctions, etc at both 1550 and 1310 nm

• Hybridized lasers at 200 kHz linewidths

• World-record bipolar amplifiers at 80+ GHz for electronic-photonic integration

OpSIS

320 Gbit/second (40Gx8) Over 1 fiber with WDM

2 km reach <10 mm2 silicon

World record transmitter (with Bergman Group, Columbia)

2.4 Tbit/second

transceiver

demonstration

in progress now

86 GHz amplifier

Telecom-grade laser

40G data

8 channel


Qianfan Xu, Rice University

Reconfigurable Optical Directed-Logic Circuits

Objective:

• Develop a scalable and reconfigurable directed

logic architecture for low-latency optical

computing.

• Demonstrate a direct logic circuit with the highly

integrated silicon photonic technology.

• Demonstrate a reconfigurable optical switch with

high speed, high extinction ratio and low

insertion loss as the basic building block.

• Develop a complete circuit simulation tool.

Approach:

• A cellular geometry with a regular row-column layout of

reconfigurable optical switches.

• Each switch has three distinctive operation modes.

• Direct mapping the truth table of an arbitrary logic function

to the operation modes of the optical switches.

• Double-ring based optical switches as the unit cell.

• A multi-spectral implementation will be realized.

• Both electro-optic and all-optical logic will be investigated.

Impact:

• Overcome the limitation of

conventional optical logic.

• Boost the performance of digital

systems for real-time applications

such as video analysis, object

recognition, missile guidance,

visualization and battle management.

• Enable highly efficient packet-switched

optical networks on chip.

• Provide a scalable platform for various

applications and for future expansion.


Experimental Demonstration

Circuits based on the multi-spectral

implementation are fabricated in CMOS

photonics foundry at IME Singapore.

Each switch has an embedded p-i-n

junction for logic input and a micro-heater

for reconfiguration.

y

l1

l2

l1

l

x1 x2

l1& l2

A 2×2 switch array can

calculate any logic function

between two logic inputs.

0 1

0 X X

1 X X

A B

Q. Xu and R. Soref, Opt. Express 19, 5244-5259 (2011) [email protected] http://www.ece.rice.edu/ece/xugroup/

fiber

ring

optical logic circuits fabricated through OPSIS program



Objective:

•Investigate the best architectural modalities to insert silicon photonic interconnect technology into systems of interest to the DOD to overcome performance and energy bottlenecks in emerging SoCs

Impact:

•This research will aim to meet aggressive ITRS data rates of multiple TB/s and a power goal of less than 1pJ/bit in multi-core SoCs, far exceeding what is possible with conventional electronics today

Approach:

•Design innovative heterogeneous network topologies and protocols that effectively combine multiple stacked layers of optical links with electrical wires

•Create new techniques for enhancing memory-access performance with optically connected DRAM and mechanisms for energy-efficient reconfiguration of opto-electronic components at run-time

Integrated Optoelectronic Networks for

Application-Driven Multicore Computing

PI: Sudeep Pasricha, Colorado State University

DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 15

SiGeSn: Basic Features and Properties

• CMOS - compatible (with SiGe); strain control,

stressors for high velocity MOSFET channels

• Variable bandgap of SiGeSn: ≈ 1.1 to 0.11 eV; (1.1 to

11 μm)

• Lattice/ strain control (aSn = 6.5 Å; aGe = 5.6 Å: aSi =

5.43 Å) (strain engineering)

• SiGeSn: highly conductive; covalent bonds; no

scattering by polar optical phonons, or Reststrahlen

absorption (limitation of III-V’s); direct bandgap (from

0.2 to 0.6 eV); enhanced luminescence; high optical

absorption; high speed (small effective mass)

Group IV

elements

Beyond Silicon Photonics - SiGeSn: a promising material system

The first group-IV material with a widely tunable 2D

compositional space, SiGeSn makes it possible to

decouple band gap and lattice constant, enabling

wide-range applications from thermal imaging to

photovoltaics to lasers


-Integrated circuits are moving to Ge-rich SiGe

materials; this requires the larger lattice constant of

GeSn for stressor layers to increase active channel

carrier mobility

-Experiments and theory suggest that Ge1-ySny has

a direct bandgap for Sn contents above 6 %

(wavelengths above 2 μm) for efficient detectors

and emitters in the mid-IR region, and compatibility

with SiGe integrated circuits. (Beyond Si Photonics)

-Mid-IR devices: GeSn provides excellent mid-IR

performance (beyond 1.8 μm limit of Ge) with possibility of

multi-pixel arrays compatible with integrated circuits and

lasers

Three prime motivators for

SixGeySn1-x-y Research

Wide Area

Motion

Imagery

Full

Motion

Video

Hyperspectral

Imagery

Enhanced

Resolution at

Range

Higher Altitude

and

Greater Standoff

Day and NIGHT

TRADITIONAL

ASYMMETRIC

HME/IED/CBRNE

Missile Warning

Active Sensor/Seeker

Detection

Pre-LaunchSensor/SeekerCountermeasure

Expendable

Post-Launch Laser

Countermeasure

Counter EO/IR Adjuncts on AAA, RF SAM, LBR, DE Weapons…

RF/EO/IR Threat Warning

and ProtectionPassive EO/IR Sensing in

Contested Environments

Laser Radar Sensing in Contested Environments

Phenomenology and

Innovative Concepts

Modeling and

Analysis

Laser Source

Research

Detector/FPA

Research

Optics/Aperture

Research

Cross-Range [m]

Ran

ge [m

]

F-4 1D Ladar Back-Projection Reconstrunction

-8 -6 -4 -2 0 2 4 6 8 10

-8

-6

-4

-2

0

2

4

6

8

10

0

20

40

60

80

100

120

140

160

180

80 100 120 140 160 180 200 220

NET

D a

t R

ange

(m

K)

Detector Operating Temperature (K)

nBn

XBn

MCT Rule 7

BLIP

InSb, 10 mm

NS4 InSb, 20 mm, 7500 ft AGL

NS25 InSb, 20 mm, 7500 ft AGL

NS25, InSb, 20 mm, 20000 ft AGL

MCT/Si

NETD Goal: 75 mK

Long Term

Concepts

[note that previous detector

arrays using III-V’s such as

InGaAs are incompatible with

SiGe circuits]


Challenges of SiGeSn

• Increase Sn content in GeSn above 14 atomic %, to study the

direct bandgap compositions, and for mid-IR operation

(present reported devices use about 4 % Sn, ~45% Sn in SiSn)

• Improve thermal stability (above 400 °C) of high Sn content

alloys for subsequent device processing (contacts, etching,

annealing)

• Identify a robust Sn source for CVD: Sn hydrides are unstable

after weeks: SnCl4 is more stable, but needs study

• Investigate fundamental properties of SiGeSn (bandgap,

mobility, carrier lifetime, electrooptic coefficients)

• World-wide, no dedicated device quality material growth

facilities available (home build CVD systems, too simple; ASM &

Applied Materials UHV-CVD, too expensive; MBE, difficult to achieve high

Sn and high quality)

• Building research teams with sufficient resources and

expertise (Kolodzey Univ of DE, Kouvetakis ASU, & Dr Bruce

Claflin WPAFB AFRL/RY developing remote-plasma-

enhanced-CVD (RPECVD) for IR application

Group IV

atoms


Results: SiGeSn Photodiode & Emitter Kolodzey Group; Univ of Delaware

• MBE growth of GeSn – up to 14.5 % Sn –

world record Sn composition in Ge lattice

• fabricated p-n GeSn/Ge heterojunctions with

good rectifying characteristics

• GeSn/Ge heterojunction photodiodes with

direct bandgap behavior for Sn above 6 %;

responsivity = 0.13 A/W for 10% Sn device

• Ge1-xSnx light emitting diode: 216 μW power;

peak emission at 2.2 μm, at T=100K with 8 %

Sn; direct bandgap behavior – (note: other

groups report uncalibrated output power)



From molecules …….

Edirect

Eindirect

Ge1-ySixSny alloys with tunable band gaps

above and below Ge

and the direct-indirect gap crossover

Below: crossover from

indirect to direct gap

semiconductor for 1st time

Left: Si4H10 (tetrasilane)

and Ge4H10

(tetragremane) molecular

sources are combined

with SnD4 to produce light

emitting direct gap

SiGeSn alloys (the

equilibrium mixture of

Si4H10 and Ge4H10

isomers are shown by the

models at left)

……to direct gap materials

Below: ASU chemical process was featured

Top: Calculated representative SiGeSn alloy

Kouvetakis, ASU

Above: first example of GeSiSn

diodes with low dark currents and

collection efficiencies up to ~80%

(better than the best GaInAsN

analogs) have been fabricated on

Ge and Si wafers.


Integrated Nanopillar Lasers and APDs for

Ultra-High-Density Optical Interconnects

• Silicon photonic systems can be densely integrated due to

tight optical confinement in silicon waveguides and mature

process technology

Problem Statement

The reduction of process complexity, improved device

performance, and device footprint can bring silicon

photonic interconnects to maximum integration density.

Relevance

Approach

• Nanopillar lasers on SOI will be:

• Electrically driven at room temperature on SOI

• Greater than 10 µW output power @ 50 µA

• Nanopillar APDs on SOI will be:

• -30 dBm sensitivity @ >10 Gb/s

Metrics / Deliverables

Device Innovations

• Integrating lasers and

detectors requires extensive

and complicated processing

• Scaling conventional planar

grown material is limited by

surface effects and cavity

geometry.

• Electrically driven micro/nano

lasers do not provide sufficient

output power to drive state-of-

the-art Ge-on-Si APDs.

• Patterned Ga(In)As(P) nanopillars grown on silicon will

simultaneously form nanopillar lasers and avalanche

photodiodes coupled to a silicon waveguides on SOI

• Difference between laser and APD is doping in silicon

• Single crystal growth step for both devices

• Fast, simple device processing after growth for rapid feedback

|E| 2 Mode:

Luxtera’s packaged

transceiver chip [1]

Bonded

InP lasers

Ge

detectors

n-Si

SOI

p-Si

Laser Detector

Nanopillars

GaP passivation InGaAs active

P+/n Si multiplier N+ Si injector

Waveguide

Output

Waveguide

Input

Prof Diane Huffaker, UCLA


1.3 µm Nanopillar LEDs

Axial/core-shell nanopillar LEDs exhibit record low leakage current

SiNx

mask

GaAs

pillar

InGaAs

insert

InGaP

shell

100 nm

p

i

n

Shapiro et al, APL 97(1), 2010. Scofield et al, Nano Lett., 2011

•IV/CV measurements show low leakage of 12 nA at -5 V

and high rectification ratios of > 10^6

•Axial InGaAs inserts are strain relaxed, emitting at 1.3 µm

Axial current injdection

with Zn and Sn doping

during growth

IV-CV measurements

on NP-LEDs Electroluminescence

at 1.3 µm

Nanopillar photonic crystal lasers are promising for high-

efficiency, high-bandwidth transceivers on silicon:


NP Arrays for Waveguides

CYTOP n = 1.34

Polyimide n = 1.7

CYTOP n = 1.34

NPs

Top-view Side-view

Design concept: “Beam” array of NPs

NP Beam arrays:

•Light is confined by NPs and polymers

•No need for precision alignment

•Can be engineered for high-Q cavities

Beam array growth:

Tilted SEM view of

4x150 NP array

Pitch = 400nm

Height = 2400 nm

10 µm


Electrical Injection Nanolaser at Room Temperature

Challenges in Nanophotonics & Miniaturization of

Semiconductor Lasers - Ning, ASU

Background

• Making a laser smaller with a total volume smaller than wavelength cubed has

been a worldwide goal for the last 5-6 years & initially thought impossible

• Other small lasers such as microcavity or photonic crystal lasers have a much

larger total volume

• Nanolasers with small total volume are expected to play an important role in

chip-scale nanophotonic integrated systems for future IT and other sensing or

detection applications

Nanolaser milestones by the Prof Ning, ASU Team: 2013- Demonstration of CW

room temperature operation with linewidth at 0.5 nm.

Silver

n-contact

n-InGaAs n-InP

InGaAs

SiN

p-InP

p-contact

p-InGaAsP

InP substrate (SEM image of etched pillar) 1500 1600 17000

10

20

30

40

92uA

316uA

618uA

1036uA

320X

80X

40X

8X

Inte

ns

ity

(a

.u.)

Wavelength (nm)

1652uA

B

B-Right: Spectra of laser output at

various injection current level under

the same conditions as in the left.

Laser intensity

in a nanolaser


Electrically Pumped Plasmonic

Nano-Laser

Program Goal:

To develop nano-scale plasmon laser

by direct electrical pumping.

Approach: Designed a waveguide

embedded (WEB) Plasmon Laser that

allows carriers to be transported in and

out-of the cavity without disturbing the well

confined plasmon modes.

Key Features

• Direct electrical modulation

• First directionally emitted plasmon laser

• Enhanced extrinsic efficiency

• Wavelength multiplexing

Motivation: enhanced light-matter interaction in nanoscale systems will enable

both ultra-small & fast laser devices at nanometer scale. Electrical operation is

vital step toward realizing practical implementation of nanoscale lasers & devices.

X. Zhang, UC Berkeley

X. Zhang, UC Berkeley


Electrical Interfaces and Modulation for

Plasmon Laser (optically pumped)

WEB plasmon laser :

• Constructed by crossing semiconductor

nanostrips over metal nanostrips with an 5-

10nm insulator gap layer

• A square shaped plasmon laser cavity at each

intersection

• Both metal and semiconductor strips can be

used as electrical contacts

Direct laser amplitude modulation with low

power consumption:

•16 dB modulation depth for a peak bias of 4V

•Opposite operation - injecting electrons and

holes into the active cavity region - can lead

to an electrically pumped semiconductor

plasmon laser

2 mm

Future: develop efficient electrical injection strategies and materials & Multiple WEB plasmon lasers at different wavelengths


FY11 MURI: Hybrid Nanophotonics

Team: Prof Mark Brongersma, Stanford Univ, PI & team lead; Zhang – UCBerkeley; Miller

& Fan – Stanford; Shalaev - Purdue; Atwater & Painter – CalTech; Lukin & Park - Harvard

Objective: Explore the full potential of hybrid nanophotonic components for on

chip optical communication by combining the best aspects of metal and

semiconductor photonics

- a suite of high performance hybrid

nanophotonic devices and systems

- new simulation tools that can deal

with the hybrid/quantum nature of the

components

- new materials and “meta” building

blocks for hybrid devices and systems

-new optical characterization tools to

analyze hybrid devices with nano-

scale resolution

-new fabrication techniques that

enable scalable fabrication of

complex hybrid devices

- Plasmonics for extremely light concentration and

enhancing light matter-interaction at nanoscale

- Semiconductors for active functions, quantum

behavior

scaling of photonics will enable devices and circuits that offer lower power operation, higher speed,, denser integration


Objective: Electrically-driven plasmon source

Objective – explore & develop electrically-

driven plasmon sources that via short

plasmonic waveguides can be coupled to

low loss dielectric waveguides

Key findings/Implications

Technical Approach

Embed p-GaAs /InGaAs/n-GaAs quantum well source

(lem = 970 nm) at in a plasmonic slot waveguide

Use same metals for waveguide as for electrical contacts

Exploit Purcell effect to enable effective coupling to the

emission to a single plasmonic mode

Optical simulations show possibility to effectively

couple QW emission into a plasmon slot

waveguide (>80%) Using e-beam lithography, plasmonic QW sources

coupled to plasmonic slot waveguides have been

realized

(a)

Basic, ultra-compact circuit elements have been

implemented

Brongersma Group, Stanford

(b)

(d) (e) ENZ modulator

Electrically-driven plasmon source


Objective: Hybrid Nanophotonic Photodetectors

demonstrate efficient photodetection into

subwavelength structures compatible with CMOS

processing techniques

Technical Approach

Embed a semiconductor detector in a nanometallic slit

Use same metals for contacts and optical confinement

Exploit resonances in the combined metal/dielectric

resonance to enhance absorption efficiency and allow

tunability of spectral response

Silicon fin detectors showing strong absorption near 850 nm

Good quantum efficiency in only 170 nm Si thickness

Key findings

Germanium fin detectors extend absorption beyond 1550 nm

Silicon two-fin detectors for simultaneous two color detection

David Miller Group, Stanford

1.5mm

v1

v2

Hybrid Nanophotonic

Photodetectors


Cavity-Free, Matrix-Addressable Quantum Dot Architecture for On-Chip Optical Switching

-- Rashid Zia and Arto V. Nurmikko, Brown University

Device integration enabled by the precise placement of Quantum Dots in Waveguide-Addressable Matrix.

Schematic Design of

Colloidal Quantum Dot

Optical Circuit

Architecture exploits strong localized fields from plasmonic & nanophotonic waveguides to:

(1)Direct quantum dot emission for scalable on-chip single photon sources, and

(2) Mediate strong interaction between quantum dots for low-photon number optical switches

Objective: Develop a cavity-free architecture for waveguide-integrated single

photon sources and optical signal processing at the few to single photon level.


The Scalable Approach builds on the recent development of highly-ordered colloidal quantum dot arrays in Nurmikko Lab through a two-step process of dielectric encapsulation and electrostatic self assembly.

50 nm

TEM Image of Silica-clad QD

Process allows one to exploit precision of E-Beam Lithography to position single QDs in large-scale arrays

Cavity-Free, Matrix-Addressable Quantum Dot Architecture for On-Chip Optical Switching


Cuong Dang et al., Nature Nanotechnology, Vol: 7, 335–339, (2012)

DBRs, R>99%

Threshold ~

60µJ/cm2 <N> ~

0.53 exciton

• First colloidal QD-based vertical-cavity surface-emitting laser (VCSEL)

• Very low threshold, well defined coherent beam at R,G, & B wavelengths

Demonstration of Colloidial

QD-VCSEL

Development of high-quality colloidal QDs enables new applications for these scalable materials in photonic devices.


LDOS Engineering in 1-D

Waveguides

1D waveguide thickness allows the direct emission into a desired mode.

Theory

Experiment

Pol

TE mode TM mode TE mode

Fabrication: electrostatic deposition and e-beam evaporation

Randomly oriented QDs present challenge for directing light emission.

Demonstrated that engineering the local optical environment can preferentially couple QD emission into specific modes.

Optimized a fabrication technique to safely embed QDs within high index dielectric layers for 1-D waveguides.


Robust (Statistical) Nanophotonics

by Repeatable, Scalable Emitter Integration

• Waveguide-Integrated Single Photon Sources

• Demonstrating a scalable process for embedding colloidal QDs in dielectric

waveguides

Method easily integrated with any nanofab process.

Reusable templates allow for repeated study of the same resonant nanostructure with different single emitters -- i.e. building statistical data sets without variations of fabrication errors or irregularities.

SEM images of QD integrated with gold rods

Scanning image of QD embedded waveguide


Impact and Implication for Future Work

Quantum Emitter Substrate

Silica-clad Quantum dots: 1.7-3.5 NV center nano-diamond: ~3 Defects in ZnO nano-crystal: 8.7-10.3 Transition metal ions doped MgO nano-cube: 12-13

VO2: 1-2

Quartz(SiO2): 1.7-3.5 SiC: 2-3.5 ITO: ~6 Sapphire(Al2O3): 7~9 Y2O3: 7~9 Si3N4: ~9 MgO: 12-13

Isoeletric Point (IEP) of different materials

The electrostatic self-assembly technique can be easily extended to other quantum emitters and material systems. By choosing proper materials for the patterns and substrates, one can precisely place various single quantum emitters.


Technology Transitions

Technology Transitions

• Students to Intel, Professor to Max Planck Institute

• Nanomembranes: MURIs ended late 2013

– Flexible Electronics – electronic tattoos, nano-printing tech:

Other AF interest (Air Combat Command, SMC)

– USDA Forest Products Laboratory - High-speed flexible

electronics on nanofibrillated cellulose (NCF) substrate

– STTRs: SysteMech, Omega, Semerane

• EM Photonics: Scalable Reconfigurable Chip-Scale Routing

Architecture to spin-off Lumilant, with subsequent transition to

JSF-F35 components

• Capasso, Harvard – Brucker - Fourier Transform Spectrometers

Utilizing Mid-Infrared Quantum Cascade Lasers

• Abeam Technologies - Spectrometer –digital planar holography

http://abeamtech.com/


- Nanophotonics more

---- Plasmonics, Nonlinear, MetaPhotonics

---- Chip-scale, 3D, computation

---- 2D materials

- Integrated Photonics, Silicon Photonics more

- Reconfigurable Elec/Photonics lower

- Quantum Computing w/ Optical Methods (QIS) const

- Nanofabrication (MURI, OSD & AFOSR STTR) lower

- Terahertz Sources & Detectors zero out

- Microwave/Millimeter Wave photonics change

Interactions - Program Trends

AFRL – RY, RI, RX, RV, RW, 475th/RH

AFRL – HPC Resources

EOARD – Gonglewski & LtCol Pollak

AOARD – Mah, Caster, Hong, LtCol

Low

SOARD – Fillerup, Pokines

ONR, ARO – MURI etc eval team

AFOSR POs

RTX: Weinstock, Curcic, Nachman,

Parra, Schlossberg, C. Lee,

Harrison, Bonneau, DeLong, Sayir

RT Special Programs: Lawal, E.

Lee, Marshall

Fed Agencies: NSF, DOE, NASA etc



Conclusion & Future

Key Program ideas, thrusts, and challenges: Plasmonics & Metamaterials/ Metasurfaces/ Meta Photonics

Bandgap engineering, Strain engineering, Index of refraction eng.

Subwavelength - Operating beyond the diffraction limit; hole transmission

Optomechanics; Single photon device concepts; quantum dot devices and

architecture; Optoelectronics of 2D materials beyond graphene

Integrated photonics & establishing a shared, rapid, stable shuttle process

for high-complexity silicon electronic-photonic systems (MOSIS model)

STTR Need: Integrated Silicon Photonics, Photonics Fabrication &

Packaging, SiGeSn material development

Transformational Opportunities Reconfigurable chip-scale photonic; mmW & RF photonics;

Integrated photonics circuits

Integrated Photonics: Engine for 21st Century Innovation –

foundation for new IT disruptive technologies

Future: Metasurfaces/ Meta Photonics, Quantum Integrated

Nanophotonics, Ultra Low Power, Graphene & 2D Beyond graphene

Optoelectronics, 3D Photonics


Close coordination within AFRL, DoD, and 26 federal agencies as NSET

member to the National Nanotechnology Initiative (NNI)

http://www.nano.gov/partners

http://www.nano.gov/initiatives/government/signature

Close coordination with the National Photonics Initiative NPI

http://lightourfuture.org/

AFOSR is the scientific leader in Silicon Photonics, nanophotonics,

nanoelectronics, nanomaterials and nanoenergetics – one of the lead

agencies to the current OSTP Signature Initiatives “Nanoelectronics

for 2020 and Beyond” and coordinating member to “Sustainable

Nanomanufacturing”

Optoelectronics & Photonics Nanophotonics, Plasmonics, Integrated & Silicon Photonics

Demo’d first plasmonic all-optical modulator, plasmon enhanced semiconductor

photodetector, plasmon laser, superlens, hyperlens, plasmonic solitons, slot

waveguide, “Metasurface” collimator etc

Conclusion & Future (cont.)

http://www.nano.gov/partners

http://www.nano.gov/initiatives/government/signature

DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 39 DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 20 February 2014

[email protected]

1 DISTRIBUTION A: Approved for public release; distribution is unlimited. 20 February 2014

Integrity Service Excellence

Gernot Pomrenke

Program Officer - Caretaker

AFOSR/RTD


GHz-THz Electronics

March 2014

2 DISTRIBUTION A: Approved for public release; distribution is unlimited.

2014 AFOSR SPRING REVIEW

NAME: Gernot Pomrenke / Jim Hwang/ Kitt Reinhardt

BRIEF DESCRIPTION OF PORTFOLIO: GHz-THz Electronics

LIST SUB-AREAS IN PORTFOLIO:

I. THz Electronics – Material and device breakthroughs for transistors based on conventional

semiconductors (e.g., group IV elements or group III-V compounds with covalent bonds) to

operate at THz frequencies with adequate power. Challenges exist mainly in perfecting

crystalline structure and interfaces.

II. Novel GHz Electronics – Material and device breakthroughs for transistors based on novel

semiconductors (e.g., transition-metal oxides with ionic bonds) to operate at GHz

frequencies with high power. Challenges exist mainly in controlling purity and stoichiometry,

as well as in understanding doping/transport.

III. Reconfigurable Electronics – Material and device breakthroughs for meta-materials,

artificial dielectrics, ferrites, multi-ferroics, nano-magnetics, and micro/nano

electromechanical systems to perform multiple electronic, magnetic and optical functions.

Challenges exist mainly in understanding the interaction between electromagnetic waves,

electrons, plasmons and phonons on nanometer scale.


I. THz Electronics

DARPA

DARPA

ONR III-N THz

ONR DEFINE

AFOSR

X’tal

Reliability

•Sub-millimeter-wave radar & imaging

•Space situation awareness

•Chemical/biological/nuclear sensing

•Ultra-wideband communications

•Ultra-high-speed on-board and

front-end data processing

Intel

IBM

Cutoff Frequency

(Po

wer)

THz


Intel’s High-k FinFETs

Pro

du

cti

on

De

ve

lop

me

nt

Channel

Source Drain

Gate

Stack

e

S

d

k

V

QC 0


Challenges for THz Electronics

•Highly strained

growth

•Single-phase

ternary

•P doping


Covalent Semiconductors

Covalent Semiconductors


InAlN Molecular Beam Epitaxy Jim Speck, UC Santa Barbara

X-ray diffraction confirms lattice match Cross-sectional transmission electron

microscopy reveals columnar structure

17% In mole fract.

140nm thickness

Scanning transmission electron

microscopy shows nano-network

Atomic probe confirms

composition variation

GaN

peak

•First extensive study of phase

separation in nitrides

•Nano-network may be useful for

thermoelectrics

•Homogeneous InAlN grown by

NH3 MBE and MOCVD perhaps by

suppressing In ad-layer at higher

growth temperatures


P-Doped InGaN Alan Doolittle, Georgia Tech

GaN:Mg Constant resistivity when

doped 1019/cm3

GaN

GaN

GaN

GaN

GaN

In0.4Ga0.6N

In0.2Ga0.8N

Objective: P-type GaN or InGaN for HBT

Approach: Optimize MBE temperature and flux to prevent surface

segregation/decomposition & to provide optimum Mg substitutional sites

Results: Breakthrough in single-phase, high-quality InGaN doped with

1020/cm3 Mg and >50% temperature-independent activation

Plan: Mitigate electrical leakage via metal-decorated dislocations


Hot Electrons/Phonons in GaN Hadis Morkoc, Virginia Commonwealth

Pla

sm

on

Reso

nan

ce

P

eak

Ve

locit

y I ~ nv

Optimum electron

concentration for

plasmon resonance

and optical-acoustic

phonon decay

2700K Electrons

Acoustic

phonons

2400K

optical

phonons

Power Supply

300K heat sink

Objective: Optimize electron density

Approach: Understand interaction of hot

electrons and phonons

Result: Explained limits of many GaN devices

Plan: Dual-well channel


Limit of AlN/GaN HEMTs Grace Xing & Debdeep Jena, Notre Dame

Regrown contact with Rs<0.1Ω-mm

Reduce

gate length Control

surface

states

Increase 2DEG mobility

Add AlN back barrier

Year

Speed (GHz)

400

600

‘11 ‘10 2007

200

‘09

NiCT

HRL MIT

Notre Dame

‘12

Objective: THz AlN/GaN HEMTs

Approach: Outlined below

Results: 370GHz cutoff frequency

Plan: Verify/improve phonon-

limited velocity model


II. Novel GHz Electronics

DARPA

DARPA

ONR III-N THz

ONR DEFINE

ZnO MOSFET

AFOSR

Nano-Oxide

DARPA

MESO

ONR

Extreme E

ARO

Interact TI

ONR

Coupled Φ

NSF

DMR

DTRA

Rad-Hard E

Industry

Thin-Film E

AFOSR

X’tal

Reliability

IBM

Intel

Breakdown,

Power

Cutoff Frequency


Ionic vs. Covalent Semiconductors

Covalent Semiconductors •Transparent Electronics: ZnO, MgO, InGa3Zn5O5

•Heterojunctions: MgZnO/ZnO, LaAlO3/SrTiO3

•Multiferroics: BiFeO3, EuO,

•Metal-Insulator Transition: VO2, SmNiO3, NdNiO3,

•Topological Insulators: Bi2Se3, Bi2Te3, Bi1-xSex,

•Other Chalcogenides: sulfides, selenides, tellurides


Challenges for THz Electronics

•Highly strained

growth

•Single-phase

ternary

•P doping


Merits of Ionic Semiconductors

Covalent Semiconductor

Ionic Semiconductor

Mo

bilit

y

Ionicity

Ionic Covalent

•Less demanding on crystalline perfectness

•Deposition on almost any substrate at low temp.

•Radiation hard, fault tolerant, self healing

•High electron concentration with correlated transport

•Metal-insulator transition with high on-off ratio

•Wide bandgap for high power and transparency

•Topological effects

•SWAP-C and conforming

Challenges

•Composition and

purity control

•Transport not well

understood


Transport in ZnO Dave Look, Wright State

24

26

28

30

32

0 100 200 300

m*0.30

0.34

0.40

Fitting parameters:

ND = 1.45 x 10

21 cm

-3

NA = 1.71 x 10

20 cm

-3

m* = 0.34m0

T (K)

(

cm

2/V

s)

Pulse Laser

Deposition

in Ar

SIMS

Positron

Kane model

•[VZn ] = 1.7x1020

cm-3 gives

E(formation) =

0.2 eV; provides

accurate check

on theory (DFT)

•Reduced [VZn ]

with Zn anneals:

got = 1.4x10-4

-cm, 3rd best in

world

•Future: create

GaZn donors by

filling VZn with Ga

•Future: apply

methods to other

TMOs

µ (ND, NA, m*, T)

Mobili

ty


LG=1.2m

Grain

Boundaries

Nanocrystalline

ZnO

PLD

World’s 1st microwave thin-film transistor

ZnO Thin-Film Transistors Burhan Bayraktaroglu, AFRL/RYDD

Record Performance

150°C deposition

110 cm2/V.s electron mobility

875mA/mm current density

9.5W/mm dc power density

1012 on/off ratio

60mV/dec sub-threshold slope

10 GHz cut-off frequency

Plan

•Room-temp.

deposition

•High-k gate

insulator

•MgZnO/ZnO

hetero-

junction

Objective: Exploit unique electronic

properties of nanocrystalline ZnO films

Approach:

•Theoretical doping & mobility models

• Pulsed laser deposition (PLD)

• Ga doping in Ar at low temperatures


Correlated Oxide Field-Effect Devices Shriram Ramanathan, Harvard

Estimated

power-delay

product

VO2 Mott FET

vs. Si MOSFET

MBE

SmNiO3

LaAlO3

Temperature (°C)

Objective: Fundamental understanding of field-effect

switches utilizing ultra-fast (ps) reversible metal-

insulator (Mott) transition in correlated oxides

Approach: Fabricate field-effect transistors with oxide

channels and investigate device characteristics

Result: High-quality SmNiO3 grown by molecular-

beam epitaxy on LaAlO3 for room-temperature

transition

Plan: Electronic transport measurement on thin-film

hetero-junctions of different oxides


III. Reconfigurable Electronics

Challenges: Understand

interaction between

electromagnetic waves,

electrons, plasmons and

phonons on nm scale

•Multiple electronic, magnetic and optical functions for UAV/MAV

•Meta-materials, artificial dielectrics, ferrites, multi-ferroics, nano-magnetics, MEMS/NEMS


EuO-Based Multiferroics Darrell Schlom, Cornell

= 0.6eV

Andreev reflection of

>96% spin-polarized

carriers from EuO to Nb

0

0.5

1

20 40 60 80 100 120 140

No

rma

lize

d M

ag

ne

tizati

on

(a.u

.)

Temperature (K)

5% La-doped

5% Lu-doped

5% Gd-doped

Insulator

Metal

Fe

rro

ma

gn

eti

c

Pa

ram

ag

ne

tic

Objective: Enhance and

exploit exceptional

spintronic, optical, and

magnetic properties of

EuO, including highest

∆R/R of any metal-insulator

transition, greatest spin-

splitting of any

semiconductor, and 2nd

highest of spin

polarization.

Approach: Reduce defects

in EuO films to enable

controlled doping.

Combine strain and doping

to boost Curie temperature.

Results: Demonstrated

controlled rare-earth

doping of EuO.

Plan: Apply misfit strain to

boost Curie temperature


Topological Insulators Yoichi Ando, Osaka U.

Unexpected

mass

acquisition of

Dirac fermions

on TlBi(S,Se)2

Phenomena:

• Insulating bulk with metallic surface

•Massless Dirac fermions

high-mobility transistor

•Dissipationless spin current

Low-loss spintronics

Objectives:

•To explore novel physics

•To minimize bulk current

•To discover better TI materials

•To detect surface spin currents

Approaches:

•Explore ternary chalcogenides

•Fabricate TI-ferromagnet devices

•Precise transport measurements


Collaboration

• AFOSR

• Gernot Pomrenke – THz optics, microwave photonics, reconfigurable electronics &

photonics (ex. TMO)

• Harold Weinstock – Nanoscale oxides

• AOARD - Seng Hong – Osaka U., Ken Caster & Misoon Mah – 2D materials

• EOARD – SPI Lithuania

• ONR

• Paul Maki – GaN

• ARO

• Marc Ulrich – Physics of topological insulators

• DARPA

• Dan Green – high overlap of interest (NEXT)

• Bill Chappell – Adaptive RF technology, RF-FPGA

• DTRA

• Tony Esposito & Kiki Ikossi – THz applications

• NSF

• Samir El-Ghazaly – THz electronics

• Anu Kaul – 2D materials & devices beyond graphene (Joint Program Initiated)


I. Covalent Semiconductors • Transition bulk growth and reliability projects via STTRs

• Push to THz via highly-strained thin-film growth, surface

passivation, and high-k gate stack

II. Ionic Semiconductors • Push oxide electronics to high GHz range

• Emphasize thin-film heterostructures

• Explore extreme carrier concentration

• Understand and overcome mobility limitation

• Explore metal-insulator transition & topological insulators

III. Reconfigurable Electronics • Plans for buildup program

Take Away Messages

High-k Gate

Multi-Ferroics

Complex

Oxides

Oxide Electronics

IV. Opportunities: 2D electronics, SiGeSn electronics

optoelectronics & photonics

Documents