Stanford University. MOCVD growth of III-V & III-N nanostructures, thin films and heterostructures

Transcription

1 MOCVD growth of III-V & III-N nanostructures, thin films and heterostructures

2 Outline MOCVD introduction MOCVD capability in SNF Work done in MOCVD lab 1. Nanostructures Catalyst free periodic nanoarrays Self-catalyzed nanostructures Gold catalyzed nanowires 2. Thin films and heterostructures GaN and AlGaN/GaN HEMT Single crystal III-V film Amorphous III-V film 2

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4 GaN growth for example: 4

5 Overview of Epitaxy Techniques Technique Strengths Weaknesses HVPE (hydride vapor phase epitaxy) MBE (Molecular beam epitaxy) MOCVD (Metal Organic Chemical Vapor Deposition) 1. Well developed 2. Large scale 1. Simple process 2. Uniform, abrupt interface 3. In-situ monitoring 1. Most flexible: Large scale production; Abrupt interface, high grown layers quality; Different materials grown in the same system; 2. Faster growth rate than MBE, costeffective; 3. Presicion in deposition thickness, suitable for MQW; 4. High growth temperature, thermodynamically favorable; 5. Selective in situ monitoring 1. No Al alloys 2. Complex process/ reactor control difficult 3. Hazardous sources 1. As/P alloy difficult 2. Expensive 3. Low throughput 1. Expensive sources 2. Most parameters to control accurately 3. Hazardous precursors /4/7

6 Device application background LED Laser Full spectrum solar cell Street light Display Decoration Traffic indicator Indoor illumination HBT&HEMT Advertisement New sensor systems for extreme harsh environments /4/7

7 Outline MOCVD introduction MOCVD capability in SNF Work done in MOCVD lab 1. Nanostructures Catalyst free periodic nanoarrays Self-catalyzed nanostructures Gold catalyzed nanowires 2. Thin films and heterostructures GaN and AlGaN/GaN HEMT Single crystal III-V film Amorphous III-V film 7

8 III-N system (AIX CCS 3x2 ) Sample size: 1x4, 3x2 wafer, pieces Temperature: up to 1300 o C TMIn TMGa TMAl TEGa NH3 InN GaN AlN InGaN Ternary, Quaternary compounds Cp 2 Mg P-type doping SiH4 N-type doping 8

9 III-V system (AIX 200/4) Sample size: 1x4, 1x2 wafer, pieces Temperature: up to 800 o C TMIn TMGa TMAl TBAs InAs GaAs AlAs TBP InP GaP AlP Ternary, Quaternary, Quinary compounds Dilute nitride of above UDMHy compounds DMZn SiH4 P-type doping N-type doping 9

10 Outline MOCVD introduction MOCVD capability in SNF Work done in MOCVD lab 1. Nanostructures Catalyst free periodic nanoarrays Self-catalyzed nanostructures Gold catalyzed nanowires 2. Thin films and heterostructures GaN and AlGaN/GaN HEMT Single crystal III-V film Amorphous III-V film 10

11 Catalyst free GaAs NW arrays with different lengths/periods Tilt 45 o 500nm 50~100nm length, 400nm period 1μm 500nm length, 400nm period Tilt 45 o 11 1μm 775nm length, 550nm period 1μm 2.9μm length, 550nm period

12 Indium ND arrays with different diameters/periods 2um 500nm 1μm 1μm 175nm diameter, 400nm period ~233nm diameter, 400nm period 299nm diameter, 550nm period 2μm 1μm 2μm ~400nm diameter, 550nm period 560nm diameter, 1μm period 776nm diameter, 2μm period 12

13 Self catalyzed nanostructures Plan view 2μm 1μm Cross section 2μm Indium self catalyzed In x Ga 1-x N graded Nanorod on GaN/Si(111) 1μm Images from Feng Zhan & Antony Jan Zinc assisted indium self catalyzed InGaAsN quaternary Nanowire on GaAs(100) 13

14 Gold catalyzed vertical NW buddles Binary NWs Ternary NWs GaAs NW on GaAs AlGaAs NW on GaAs 2μm GaAs NW on Si AlGaAs/InGaP core shell 500nm 1μm 500nm Images from Yangsen Kang 14

15 Gold catalyzed horizontal NWs GaAs NW/GaAs(100) 5μm 500nm 60nm diameter, 2-3μm long 15

16 Application 1: Optical Absorption Enhancement in Freestanding GaAs Thin Film Nanopyramid Arrays Experimental measurement of absorption on 160 nm thick GaAs nanopyramid film and on 160 nm GaAs planar film at incident angles of 10 o, 40 o, and 80 o. 16 a) 650 nm diameter silica nanospheres assembled into a close packed monolayer on an epi-ge substrate. b) Shrunk nanospheres. c) Ge nanopillars. d) Ge nanopyramids. e) 45o view of GaAs-Ge core-shell nanopyramids. f) Top view of GaAs-Ge core-shell nanopyramids. g) Front side morphology of a freestanding GaAs nanopyramids fi lm. h) Backside morphology of GaAs nanopyramid film on PDMS superstrate Liang et al., Adv. Energy Mater. 2012, 2,

17 Application 2: Growth mechanism and photoelectrochemical properties of conical InP and InN nanowires InP NW InN NW Gold-catalyzed InN NW Indium-catalyzed InN NW 17 InP nanowires can support a reduction photocurrent analogous to the hydrogen evolution reduction in photoelectrochemical water splitting InN nanowires support an anodic photovoltage that serves as a template for investigations into high-indium InGaN alloys for photovoltaics Vijay Parameshwaran et al., Nano Lett., under review.

18 Outline MOCVD introduction MOCVD capability in SNF Work done in MOCVD lab 1. Nanostructures Catalyst free periodic nanoarrays Self-catalyzed nanostructures Gold catalyzed nanowires 2. Thin films and heterostructures GaN and AlGaN/GaN HEMT Single crystal III-V film Amorphous III-V film 18

19 Demonstrated high quality GaN on Sapphire growth GaN on Sapphire (0002) GaN Sapphire (0002) Images from Garrett Hayes 19

20 GaN on Si(111) GaN Al 0.2 Ga 0.8 N Al 0.5 Ga 0.5 N Al 0.8 Ga 0.2 N AlN 1x1μm 10x10μm 20

21 Application: AlGaN/GaN HEMT on Si Barrier Al Composition Wafer size high uniformity Wafer Thickness Built-in potential measured by LEI OCV (open circuit voltage): Vbi distribution across wafer diameter Vbi is correlated with sheet carrier density Ave= Stdev%=6.2%

22 Application: AlGaN/GaN HEMT on Si Wafer size high uniformity Sheet resistance Ave= Stdev%=8.9% Sheet resistance 2DEG Mobility #31 #32 #33 #34 #35 Average (cm 2 /Vs) Stdev% µ 1 (cm 2 /Vs) µ 2 (cm 2 /Vs) µ (cm 2 /Vs) % Ave= Stdev%=2.9% LEI Contactless sheet resistance scan 22

23 Application: AlGaN/GaN HEMT on Si Barrier Al%=26.3% High 2DEG mobility Barrier Al%=38.2% Electrical performance: Al% Mobility (cm 2 /Vs) Sheet Number (cm -2 ) Sheet Resistance (ohm/cm 2 ) 26.3% E % E

24 Single crystal III-V film growth GaAs/AlAs on GaAs (100) GaAs Fringe area AlAs GaAs (100) Images from Yangsen Kang 24

25 Single crystal III-V film growth GaAs InGaAsN GaAs Garrett J. Hayes et al., MRS Communications (2015). 25

26 Application: InGaAsN for laser liftoff of GaAs thin films As grown After laser melting Garrett J. Hayes et al., MRS Communications (2015). 26

27 Application: InGaAsN for laser liftoff of GaAs/InGaP heterojunction GaAs InGaP InGaAsN InGaP 1μm GaAs substrate 200nm Images from Antony Jan & Ben Reeves 27

28 Amorphous III-V film growth Amorphous InAs grown at 300 o C GaAs film on Si grown at 600 o C InAs/dielectric GaAs/Si 500nm 1μm Pt InAs dielectric Si 1μm Pt GaAs Si 1μm Images from Xue Bai 28

29 Application: Recrystallize Amorphous InAs with Rapid Melt Growth process RMG stripe Si Substrate Si Substrate Si Substrate Si Substrate Flexibility of deposition techniques High throughput Minimum materials usage Multiple materials integration Low defect density 300mm compatibility Si Substrate cooling/crystallization Si Substrate Rapid thermal annealing (Chen. 2010) Perfect crystal Dislocations Schematics from Xue Bai 29

30 Application: Recrystallize Amorphous InAs with Rapid Melt Growth Process SEM InAs Si Substrate EBSD SEM In Ga As EBSD InAs dielectric Interfacial layer Si substrate InAs has eutectic point with Si Eutectic point melts both Si and InAs much lower than the melting temperature of InAs and Si Polycrystalline InAs stripes due to Si incorporation GaAs as the interfacial layer GaAs has an eutectic point with Si higher than InAs melting temperature. High yield, >90% stripes are (100) oriented 30 Images from Xue Bai

31 Acknowledgements The speakers: Dr. Maxim Kelman, AIXTRON; Prof. Debbie G. Senesky, Stanford; Mr. Torsten Stoll, Nanometrics; Dr. Mark Benjamin, Lehighton Electronics; Dr. Ryan Zhong from Aixtron for HEMT recipe tuning; Dr. Zhiqiang Li and Mr. Torsten Stoll from Nanometrics for PL and thickness mapping; Dr. Mark Benjamin from LEI for OCV and sheet resistance mapping; Prof. Senesky and her group: Caitlin Chapin, Ateeq Suria, Hongyun So et al. for process support; Students working on MOCVD community service project: Caitlin Chapin, Seonghyun Paik, Jieyang Jia, and Sam Falkenhagen for process support; MOCVD users: Xue Bai, Vijay Parameshwaran, Antony Jan, Ben Reeves, Garrett Hayes, Feng Zhan, Yangsen Kang, Dong Liang for sharing experimental results 31