Quantum Wells/Dots and Nanowires for Optoelectronicdevice

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�� The Australian National University Research School of Physical Sciences and Engineering

QuantumQuantum Wells/DotsWells/Dots andand NanowiresNanowires forfor OptoelectronicOptoelectronic DeviceDevice ApplicationsApplications

Michael Q. Gao, H. Hoe Tan, Chennupati Jagadish ([email protected])

Department of Electronic Materials Engineering Research School of Physical Sciences and Engineering The Australian National University, Canberra, Australia

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering The Group

Few people are missing (M. Buda, Y. Kim, Q. Gao, J. Wong-Leung, H. Hattori) Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Overview • Introduction • Growth of Quantum Dots by Metal Organic Chemical Vapour Deposition (MOCVD) • Towards Quantum Well/Dot Photonic Integrated Circuits – Intermixing (QW/QD) by ion implantation ¾ Quantum Well/Dot Lasers ¾ Quantum Well/Dot Infrared Photodetectors (QDIPs) • Carrier lifetime Modification by Ion Implantation for untra-fast detectors and THz emitters • Nanowires • Summary

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Overview • Introduction • Growth of Quantum Dots by Metal Organic Chemical Vapour Deposition (MOCVD) • Towards Quantum Well/Dot Photonic Integrated Circuits – Intermixing (QW/QD) by ion implantation ¾ Quantum Well/Dot Lasers ¾ Quantum Well/Dot Infrared Photodetectors (QDIPs) • Carrier lifetime Modification by Ion Implantation for untra- fast detectors and THz emitters • Nanowires • Summary

Department of Electronic Materials Engineering Optoelectronics

Compound Semiconductors – GaAs, GaP, GaN, AlAs, InAs, InP, InN, AlN, ZnO

LEDs for Lighting Applications J. Pankove I. Akasaki S. Nakamura

II III IV V VI Be B C N O Mg Al Si P S Zn Ga Ge As Se Cd In Sn Sb Te Source: Osram, Corning, Sony, Jim Harris, Joe Campbell Corning, Sony, Jim Harris, Joe Source: Osram, Department of Electronic Materials Engineering Hg Tl Pb Bi Po The Australian National University Research School of Physical Sciences and Engineering Optical Fiber Communications

Lasers, Modulators, Photodetectors 1310 and 1550 nm

Wavelength Division Multiplexing

Single Channel Optical Link The Australian National University Research School of Physical Sciences and Engineering High Density Data Storage / Entertainment

CDs (780 nm - Infrared)

DVDs (650 nm - Red)

HD-DVDs (405 nm- Violet)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Infra-red Photodetectors

Long-wavelength infrared radiation detection (2-30µm): – Applications • Thermal imaging, night vision, space ranging, thermal analysis, atmospheric sensing – Type of semiconductor detectors • Intrinsic: HgCdTe, InSb, PbS, PbSe • Extrinsic: Si:In, Si:Ga, Si:As • Intersubband transition (III-V): QWIPs – Advantages of QWIPs (and QDIPs) • Mature epitaxial and fabrication technologies • High degree of uniformity • Easy to fabricate large arrays and monolithic integration • Lower cost

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering How a Semiconductor Laser Works?

Current

p p n n Z

Zhores Alferov, Z Herbert Kroemer, 1963 2000 Nobel Prize for Physics

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering How a QW/QD Infrared Detector (QDIP) Works?

Excited state photocurrent n Bound state

incident infrared radiation

GaAs Substrate

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Why Quantum Dots?

3D Carrier Confinement in QDs Leads to Atom-Like Density of States

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering QD Optoelectronic Devices

• Lasers

– reduced threshold current Current p – increased differential gain (gain per i injected electron) n – less temperature sensitive threshold current and emission wavelength – longer wavelength VCSELs (1.3 and 1.55 um)

• Infrared Photodetectors (Inter sub-band) – normal incidence operation – higher detector responsivity – higher operating temperature QDIPs: Normal incidence detection Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Overview • Introduction • Growth of Quantum Dots by MOCVD • Towards Quantum Well/Dot Photonic Integrated Circuits – Intermixing (QW/QD) by ion implantation, IFVD ¾ Quantum Well/Dot Lasers ¾ Quantum Well/Dot Infrared Photodetectors (QDIPs) • Carrier lifetime Modification by Ion Implantation for untra-fast detectors and THz emitters • Nanowires • Summary

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Self-assembled Growths of Quantum Dots

Frank-van der Merwe Volmer-Weber Stranski-Krastanow

Layer by Layer Direct Island Layer by layer, then Island Lattice Large lattice nucleation matched mismatch systems Very high interfacial Dissimilar lattice spacing, low (AlGaAs on energy GaAs) interfacial energy (GaN on Sapphire) (In(Ga)As on GaAs)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Metal Organic Chemical Vapour Deposition (MOCVD)

Ga(CH3)3(g) + AsH3(g) o GaAs(s) +3CH4(g)

In(CH3)3(g) + AsH3(g) o InAs(s) +3CH4(g)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Molecular Beam Epitaxy (MBE)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering MOCVD - high T growth and lack of in-situ monitoring

• Aixtron 200/4 MOCVD reactor

• TMGa, TMAl, TMIn, AsH3,PH3 (Dissociation of gases)

• In0.5Ga0.5As, InAs Quantum dots • Dot growth ~500-550°C, Other layers at 600-650°C • AFM (surface dots) and PL (buried dots)

InGaAs or GaAs 30nm InAs QDs or InP

GaAs 30nm or InP

GaAs or InP Substrate

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Growth Parameters

Amount of Material (Size and Density) Growth Temperature (Adatom Mobility, Size & Density) Growth Rate (Size and Density) V/III Ratio (Adatom Mobility, Atomic Hydrogen)

1x1µm Desired Properties InAs/InP QDs

High density of smaller coherent islands Good size uniformity Minimize / avoid formation of dislocated large islands

1x1µm

InGaAs/GaAs QDs Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Overview • Introduction • Growth of Quantum Dots by MOCVD • Towards Quantum Well/Dot Photonic Integrated Circuits – Intermixing (QW/QD) by ion implantation ¾ Quantum Well/Dot Lasers ¾ Quantum Well/Dot Infrared Photodetectors (QDIPs) • Carrier lifetime Modification by Ion Implantation for untra-fast detectors and THz emitters • Nanowires • Summary

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Photonic Integrated Circuits / Optoelectronic

Integrated Circuits • Integrated Circuits Show Superior Performance Over Discrete Devices • Multi-functional circuits, e.g. WDM sources • Integrated Transceivers • Low Cost, Packaging

Department of Electronic Materials Engineering Optical output (to optical fibre) (to optical dielectric passivation implant isolation

WDM optical amplifier passive optical waveguides multi-wavelength laser diodes The Australian National University The Australian National Research School of Physical Sciences and Engineering Materials Engineering Department of Electronic The Australian National University The Australian National Research School of Physical Sciences and Engineering Materials Engineering Department of Electronic The Australian National University Research School of Physical Sciences and Engineering

Photonic Integrated Circuits

Different Bandgaps on the same chip

Quantum Well/Dot Intermixing / Selective Area Epitaxy Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Quantum Well/Dot Intermixing

before after

Non-uniform composition profile

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Quantum Well/Dot Intermixing

before after

•Diffusion of In and Ga across interface creates graded region in the case of GaAs/InGaAs Quantum Dots •Changes Bandgap, refractive index, absorption Coefficient

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Methods Widely Used for Quantum Well (Dot) Intermixing

Impurity Induced Disordering, e.g. Zn, Si

Impurity Free Interdiffusion, e.g. SiO2, SOG Ion Implantation Induced Interdiffusion

Defects introduced by these methods enhance atomic interdiffusion

Goals: High Selectivity and Low Concentration of Residual Defects while achieving large band gap differences

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Why Ion Implantation?

Widely used in Microelectronics Industry Defect Concentration - Ion Dose, Ion Mass, Implant Temperature, Dose Rate Defect Depth -Ion Energy Selective Ion Implantation using Masks

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Ion implantation induced quantum well/dot intermixing

Ion implantation

Vacancy Point defects: Interstitial

Intermixing

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Schematic of 4 QW structure (40 keV Proton Defect Profile)

QW1 =1.4 nm QW2=2.3 nm QW3=4.0 nm QW4=8.5 nm

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering 10K Photoluminescence Spectra

H.H. Tan et.al., Appl. Phys. Lett. 68, 2401 (1996).

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Energy Shifts vs. Proton Dose 900oC, 30 sec

QW1 =1.4 nm QW2=2.3 nm QW3=4.0 nm QW4=8.5 nm

H.H. Tan et.al., Appl. Phys. Lett. 68, 2401 (1996).

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Implantation Induced InGaAs QD Interdiffusion

Protons Arsenic Ions

1.0 as-grown as-grown 1.0 O annealed 750 C, 30s annealed 13 2 5x10 H/cm 0.8 1x1011 As/cm2 0.8 14 2 1x10 H/cm 5x1011 As/cm2 15 2 1x10 H/cm 0.6 1x1012 As/cm2 0.6 5x1012 As/cm2

0.4 0.4 Intensity (a.u.) Intensity Intensity (a.u.) Intensity 0.2 0.2

0.0 0.0 900 950 1000 1050 1100 1150 1200 900 950 1000 1050 1100 1150 1200 Wavelength (nm) Wavelength (nm)

P. Lever et al, Appl. Phys. Lett. 82, 2053 (2003)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering LowLow DoseDose –– 8080 keVkeV OO ĺĺ ZnO/ZnZnO/Zn0.70.7MgMg0.30.3OO

Implanted a-axis epitaxial MQW ZnO(2 nm)/Zn0.7Mg0.3O(5.5 nm) sample with low energy oxygen ions. Low doses in the range 5 x 1014 O-cm-2 –1 x 1016 O-cm-2

Following implantation, MQW samples were annealed for 60 s at 800 oC under Ar ambient. Energy shifts, caused by interdiffusion of Mg and Zn species between the well and barrier were observed with CL spectroscopy

Study on unimplanted MQW samples showed them to be thermally stable under this annealing regime, meaning that all observed changes arose as a result of defects introduced during implantation

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

CL spectra of O implanted ZnO/ZnMgO MQW sample implanted with varying doses of O ions and RTA at 800 oC for 60s under Ar Ambient

20000

as received 5 X 1014 O cm-2 15000 1 X 1015 O cm-2 5 X 1015 O cm-2 1 X 1016 O cm-2 10000

5000 Normalized CL intensity (arb. units) 0 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 Energy (eV)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Diffusion length, Ld and peak energy shift as a function of implantation dose

30 Mg length, L diffusion 350 MQW energy shift 28 Calculated Mg diffusion length 26 300 24 22 250 20 18 200 16 d

14 (A) =2*sqrt(Dt) 150 12 10 Energy shift (meV) shift Energy 100 8 6 50 4 2 1015 1016 Irradiation dose (O- cm-2)

V. Coleman et al, Semicond. Sci. Technol. 21, L25 (2006) Department of Electronic Materials Engineering MRS Fall Meeting 2005 EE The Australian National University Research School of Physical Sciences and Engineering

Tuning the Emission Wavelength of GRINSCH Quantum Well Lasers

GaAs/AlGaAs QW Lasers

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Multi Wavelength Lasers

p-type contact Oxide isolation QW Substrate n-type contact un-implanted dose A dose B

O1 O2 O3

dose A < dose B

O1 > O2 > O3

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Lasing Spectra and L-I Characteristics of GaAs/AlGaAs QW Lasers

(900oC, 60 sec)

H.H. Tan and C. Jagadish, Appl. Phys. Lett. 71, 2680 (1997).

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Multi-Step Implantation Scheme for Improved GaAs/AlGaAs QW Laser Performance

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Quantum Wire Lasers

Cross-sectional TEM of GaAs- AlGaAs quantum wire structure

AlGaAs barrier side wall AlGaAs barrier quantum well GaAs buffer GaAs substrate quantum wire

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Light emission from quantum wire laser array

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Tuning the Detection Wavelength of Quantum Well Infrared Photodetectors (QWIPs)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Tuning the wavelength of QWIP

Metal contact Top contact Multi-QWs Metal contact Bottom contact Substrate

un-implanted dose A dose B

O3 O2 O1

dose A < dose B

O1 < O2 < O3 Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering QWIP spectral response

1.2 un-implanted 950oC, 30 sec 16 -2 1.0 1u10 cm 2u1016 cm-2 16 -2 0.8 3u10 cm 4u1016 cm-2 L. Fu et al, 0.6 Appl. Phys. Lett. 78, 10 (2001). 0.4

Photoresponse (a. u.) 0.2

0.0 4 6 8 10 12 14 Wavelength (Pm)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Responsivity

0.13 reference 0.12 0.11 L. Fu et al, Appl. Phys. 0.10 Lett. 78, 10 (2001). 1u1016 cm-2 0.09 0.08 0.07 2u1016 cm-2 0.06 0.05 0.04

Responsivity (mA/W) 0.03

0.02 3u1016 cm-2 0.01 0.00 -3-2-10123 Bias (V)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Overview • Introduction • Growth of Quantum Dots by MOCVD • Towards Quantum Well/Dot Photonic Integrated Circuits – Intermixing (QW/QD) by ion implantation, IFVD ¾ Quantum Well/Dot Lasers ¾ Quantum Well/Dot Infrared Photodetectors (QDIPs) • Carrier lifetime Modification by Ion Implantation for untra-fast detectors and THz emitters • Nanowires • Summary

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Implantation for Ultrafast photodetector materials

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Ultrafast photodetector materials - GaAs

At low annealing temperature: • very short carrier lifetimes, • low mobility and low resistivity

At 600qC annealing: • short carrier lifetimes - ps range, 2 MeV Ga/As into SI GaAs, dose = 1x1016 cm-2 • high mobility and high resistivity

Department of Electronic Materials Engineering H.H. Tan et al., IEEE Sel. Topics Quan. Electron. 2, 636 (1996) The Australian National University Research School of Physical Sciences and Engineering Ultrafast photodetector materials - InP

-1 unimplanted value s 3 -1 V 2 2 annealed 700oC cm 3

1 o x 10

annealed 600 C eff P 0 annealed 500oC

o 3 annealed 400 C

10 Counts (a.u.)

) as-implanted -2 2

cm 10

11 un-implanted 101 (x 10

s -400 -200 0 200 400 n 100 Theta/2Theta

0 200 400 600 800 • At 600-700°C, recovered most crystalline Annealing Temperature (oC) damage and original mobility • Increased carrier concentration with 1 MeV P into SI InP, dose = 1x1016 cm-2 annealing temperature (due to shallow donors)

C. Carmody et al., J. Appl. Phys. 94, 1074 (2003) Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Ultrafast photodetector materials - InP

) 2.5 -1

s 18

-1 2.0 V 2 1.5 16 cm

3 1.0 14 0.5 12 (x10 0.0 eff P 14 10 10 8 13 ) 10 -2

Lifetime (ps) 6 o

(cm semi-insulating InP implanted at 200 C 12 4 s 10 16 -2 o N 2 to 10 cm and annealed at 600 C for 30s 11 10 0 105 1014 1015 1016

) -2 104 Dose (cm ) /

: 3 (

s 10 18 -3 R ~1.3x10 cm p -InP • By implanting into p-type, the shallow donors 2 10 ~3.4x1017 cm-3 p -InP can compensate the acceptors 1012 1013 1014 1015 1016 • Short lifetimes with high mobility and Dose (cm-2) high resistivity could be achieved

o 1 MeV P into p-type InP, annealed 600 C, 30sC. Carmody et al., J. Appl. Phys. 94, 1074 (2003) Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Ultrafast photodetector materials - InGaAs

1000 30 ) 800 -1 s

-1 25

V 600 2 400 20 (cm eff P 200 15 o 800 C, W =4.5 ps 0 10 PL o 700 C, =4.0 ps WPL 5 600 oC, =2.2 ps WPL

PL intensity, counts/s PL intensity, o 500 C, W =1.3 ps 0 PL 8 1016 cm-2 051015 20 25 6 1015 cm-2

/square) Time, ps

: 4 5 • Implantation creates shallow donors, as in InP 2 (x10 • Higher dose required to achieve high resistivity, s R 0 hence no luminescence observed due to highly defected material 0 100 200 300 400 500 600 700 800 900 • Use Fe instead as it creates a deep level Annealing temperature ( oC for 30 s) • ps lifetimes and with reasonable resistivity, mobility maybe achieved 2 MeV Fe into InGaAs C. Carmody et al., Appl. Phys. Lett. 94, 1074 (2003) Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Summary of ultrafast photodetector materials by implantation

GaAs • Relatively easy - ps lifetimes, high resistivity, high mobility • Compromise btw carrier lifetimes and resistivity/mobility

InP • Implantation creates shallow donor • Hence, need p-type material and careful control of impl. dose • ps lifetimes, high resistivity, high mobility achievable

•InGaAs • Implantation creates shallow donor • Higher implantation dose required, compared to InP (highly defective material) • By using Fe (deep trap), ps lifetimes with reasonable resistivity, high mobility achievable

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Implanted III-V Materials for THz Emitters

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering How do we define “THz Radiation”? Terahertz / sub millimetre wave / far infrared

UNITS: 1THz / 1ps / 300µm / 4.1meV / 47.6K

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Why are we interested in THz photonics? • THz spectroscopy covers energy range of correlated systems (excitons, Cooper Pairs, phonons, plasmons…) • Also energy range for molecular rotations and vibrations (plastic explosive detection) • Non-contact probe of conductivity • High resolution electric field detection in devices (chip diagnostics) • Time resolved probe of dielectric properties of materials & devices • Non ionising (medical/dental imaging) • Non destructive testing (imaging faults) • MANY MORE USES ACROSS DIVERSE FIELDS!!

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Single-cycle terahertz emitters

Bulk semiconductor Photoconductive switch emitter emitter fs laser pulse Single-cycle THz pulse

EX E

What optimization is required? Improve spectral intensity Increase bandwidth

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Ion implanted GaAs [Phys. Rev. B 70 235330; Appl. Phys. Lett. 86:254102 (2005)] • GaAs was implanted with dual, high energy doses of As+ at 1MeV and 2.4MeV, creating: – An approximately uniform vacancy damage profile – Extending over the infrared (800nm) absorption depth of GaAs total )

• Past work used low energy -3 1.2 2.4MeV 1.0MeV cm

(~200keV) As ions 17 1 [Appl. Phys. B: Lasers Opt. 72, 151; intensity J. Appl. Phys. 93, 2996] of 800nm 0.8 light • Annealed at 500˚C for 30 min to allow mobility to recover, 0.6 while retaining ultrashort 0.4 carrier lifetimes (~0.1ps) [Appl. Phys. Lett. 66 3304; 76 1306] 0.2

+ concentrationVacancy (10 •Also In0.53Ga0.47As:Fe and + 0 InP:Fe 0 0.5 1 1.5 2 Depth (Pm) Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Terahertz emission from GaAs:As+ surfaces

1MeV, 2.4MeV 4 (a) No trend low ion dose 0.25, 1x1013 cm-2 ) in peak high ion dose 15 -2 -1 1.25, 5x10 cm 2 electric field 0 geometry E(t) (Vm -2 Shorter for higher -1 -0.5 0 0.5dose samples1 1.5 2 Time t (ps) 15 IR low ion dose THz

) (b)

-1 high ion dose 10 )| (Vm

Q 5 |E( 0 0 1 2 3 4 5 6 [Phys. Rev. B 70 235330] Frequency Q (THz) Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Effects of Annealing on THz Emission

For low implant dose, annealing causes an increase in maximum THz field from 1.6 V m-1 to 3.0 V m-1, but a decrease in the frequency of peak power from 2.1 THz to 1.6 Thz.

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Overview • Introduction • Growth of Quantum Dots by Metal Organic Chemical Vapour Deposition (MOCVD) – InGaAs/GaAs, InAs/GaAs – InAs/InP, InAs/InGaAsP/InP • Towards Quantum Well/Dot Photonic Integrated Circuits – Intermixing (QW/QD) by ion implantation, IFVD ¾ Quantum Well/Dot Lasers ¾ Quantum Well/Dot Infrared Photodetectors (QDIPs) • Nanowires Single Photon Sources / Detectors Photonic Crystals • Summary

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Nanowires

Nanowire RTD (Samuelson group) Laser GaAs: 5.653 A (Lieber group) InAs : 6.058 A Si : 5. 431 A ZnO Nanowire laser (Peidong Yang, UCB)

Exploration of truly one-dimensional Heterostructure semiconductor devices InAs on GaAs (ANU)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Vapor-Liquid-Solid Growth of GaAs (111)B nanowires

(111) Axial growth Source Molecules (vapor) gold ball Molten Au:Ga Eutectic (liquid)

Hexagonal Column (solid) Adatom migration Radial growth

GaAs Nanowires grown using Gold Nanoparticles Triangular base

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Nanowires Growth Methods

Au deposition ( < 1 nm-thick)

Agglomeration by Annealing ( > 600 oC)

MOCVD • Significant diameter dispersion of nanowires growth due to random agglomeration • Poor reproducibility due to the difficulty in Au film thickness control • Possible high optical/structural quality

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Nanowires Growth Methods

Poly-L-lysine deposition Poly-L-lysine layer

Gold colloidal solution deposition

Poly-L-lysine (PLL, one of polymer electrolytes) • attracts negatively charged gold nanoparticles • prevents the agglomeration of gold nanoparticles

See the difference ! MOCVD growth

without PLL treatment with PLL treatment Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Image of a single GaAs NW PL

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering TEM of GaAs nanowire

20 nm

nm 00 54 Stacking fault

Stackingu fault A 120 nm

Sonicated GaAs nanowire grown @ 450 oC

<1 1 1 > Perfect crystalline property except stacking faults

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering InGaAs nanowires on GaAs (111)

ahigh 10 K density

Low density Intensity (a.u.)

0.7 0.8 0.9 1.0 1.1 2 Energy (eV) Pm

Y. Kim, H. Joyce. Q. Gao, H.H. Tan, C. Jagadish, M. Paladugu, J. Zou, A. Suvorova, Nano Lett. 6, 599-604 (2006)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Heterostructural Nanowires on GaAs (111)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

InAs NWs on GaAs sub GaAs/InAs NW InAs/GaAs NW

GaAs InAs

InAs GaAs

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering GaSb nanowires on GaAs (111)

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering HRTEM of GaSb/GaAs NWs

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Future: Ordered Nanowires

Porous Alumina Template

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering Summary

• Quantum Dots - strongly affected by growth conditions • MOCVD growth of Quantum Dots is challenging and promising for optoelectronic device applications • Quantum Well and Quantum Dot Intermixing Techniques are promising for Optoelectronic Device Integration • Understanding defect generation, diffusion and annihilation processes are important for achieving QWI and QDI • Carrier lifetime • Nanowires offer opportunities to develop novel nano- photonic devices, e.g. single photon sources, QD lattices, photonic crystals

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Acknowledgment

Kallista Stewart, Sudha Mokkapati, Satya Barik, Greg Jolley, Victoria Coleman, Michael Fraser, Paulus Gareso, Mykhaylo Lysevytch, Ian McKerracher, Hannah Joyce, Mohan Paladugu (UQ) Fu Lan, Jenny Wong-Leung, Yong Kim, Michael Aggett

Mike Gal, University of New South Wales Matthew Phillips, University of Technology, Sydney Zou Jin, University of Queensland A. Suvorova, University of Western Australia

Australian Research Council

[email protected]

Department of Electronic Materials Engineering The Australian National University Research School of Physical Sciences and Engineering

Department of Electronic Materials Engineering