Research Scientist - semiconductor

Yanfeng Lao, Ph.D.

**** ********* **, *******, ** 30341 (Currently relocating)

# H: 678-***-**** # O: 404-***-****

******@*****.***

Online resume: L9wiz.net/resume

** SUMMARY **

Experienced professional extremely well-versed in semiconductor physics, material growth, device modeling and development, with demonstrated success in broad-scope devices. Profound understanding of the device operating principle. Significant contributor of the vertical-cavity surface-emitting laser project and a variety of photodetectors. Professional capability of administering Molecular Beam Epitaxy in growing various compound semiconductors and devices, and cleanroom device processing. Accomplished inventor and scientist with 8 patents and 67 publications.

(SEMICONDUCTOR PHYSICS ~ DEVICE DESIGN, MODELING, FABRICATION & CHARACTERIZATION ~ EPITAXIAL GROWTH)

** AREAS OF EXPERTISE **

# Optoelectronic device

# Semiconductor laser

# Vertical-Cavity Surface-Emitting Laser (VCSEL)

# Edge Emitting Laser (EEL)

# Photodetector / Sensor

# Transparent Thin-Film Transistor (TFT)

# Epitaxial growth

# Semiconductor device physics

# Device modeling, design and development

# Compound semiconductors

# Low-dimensional quantum physics

# Quantum structures: quantum wells / dots, superlattices

# III-V wafer fab processes

# Material characteristics & modeling

# Process equipment

# Device test

# Spectroscopy: Fourier Transform Infrared (FTIR) spectrometer/ Monochromator

# Material characterizing tools

# Device characterizing tools

# Cleanroom device processing

# Programming: FORTRAN, C, C++, Mathematica

** PROFESSIONAL EXPERIENCE **

# Department of Physics and Astronomy, Georgia State University, GA

Research Scientist (2013 to Present)

# Developed a new type hot-carrier photodetector based on a hot-cold carrier energy transfer mechanism; capable of detecting radiation in the wavelength range (up to THz) longer than the traditional spectral limit.

# Accomplished photodetectors with a non-symmetrical energy band configuration, operating in the photovoltaic mode and extended wavelength range.

# Developed high-performance p-type quantum dot photodetectors based on valence-band intersublevel transitions, operating in the mid-infrared range, and also achieved strong THz response at high temperatures (up to 130 K).

# Invented internal photoemission spectroscopy (IPS) for characterizing materials and detector devices, for example, type-II InAs/GaSb superlattice, HgCdTe, GaAs/AlGaAs photodetectors and so on.

# Fundamental researches of the IPS method on resolving the valence-band Van Hove singularity and identifying phonons participating in indirect optical transitions, showing advantages compared to the traditional approaches.

# Department of Physics and Astronomy, Georgia State University, GA

Postdoctoral Research Associate (2009 to 2013)

# Developed novel p-GaAs photodetectors utilizing p-type valence-band transitions for high-temperature operation; the results are advantageous for designing multi-spectral detection based on the single p-type GaAs structure

# Achieved room-temperature photovoltaic photodetectors owing to non-symmetrical carrier transport without an applied bias voltage with minimizing detector noise that enables high-temperature operation.

# Skillfully researched and achieved a variety of optical modeling approaches: 1) optimizing detector performance by enhancing the absorption of detectors and utilizing accurate optical constants; 2) full-spectral-range dielectric function (from UV to IR); 3) a universal fitting algorithm to extract optical constants of materials based on experimental optical spectra (e.g., reflection / transmission / absorption);

# Developed the fundamental theory for the internal photoemission based characterizing tool and successfully applied to probing the temperature dependency of semiconductor band offsets.

# Theoretical design of high quantum efficiency detectors by enhancing optical coupling; simultaneous improvement of the multi-band absorption efficiency by a resonant cavity structure is achieved.

# Leveraged strong expertise in developing multiple programs (FORTRAN, C, C++, Mathematica etc) encompassing spectral response simulation, optical spectral fitting, internal photoemission fitting, k•p energy band structure computation, transfer matrix method, Kramers-Kronig transform, Levenberg-Marquardt minimization fitting algorithm, multiple oscillator model for extracting optical constants and so on.

# Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai

Assistant Research Fellow (2003 to 2009)

# Developed (principle investigator) 1.31 µm vertical-cavity surface-emitting laser (VCSEL): device design (InAsP/InGaAsP quantum wells, InP- and GaAs-based and TiO2/SiO2 Distributed Bragg reflectors (DBRs), cavity modeling, computation of electrical and optical characteristics), epitaxial growth, material characterization, wafer fusion, device processing and characterization.

# Innovatively invented the wafer fusion technique to integrate GaAs- and InP-based semiconductor materials.

# Administered Molecular Beam Epitaxy (Gas Source VG V90 system) and grew a variety of compound semiconductors and device structures: GaAs- and InP-based III-V semiconductors, DBRs, InAsP/InGaAsP VCSELs, InAsP/InGaAsP edge emitting lasers, InAs/InP quantum dot lasers, type-II InAs/GaSb photodetectors, InP/AlInAs tunnel junctions etc.

# Implemented transparent thin-film transistor (TFT) with ZnMgO used as the gate insulator and channel.

# Developed 1.55-µm InAs/InP quantum dot lasers operating at room temperature and continuous-wave conditions.

# III-V wafer fab processes & characterizing tools: Photolithography, Wet and dry etching, Plasma-enhanced Chemical Vapor Deposition (PECVD), Electron-beam and ion-beam sputtering deposition, Current-Voltage Temperature (I-V-T) and Light-current-voltage (L-I-V) characteristics, Electrochemical C-V profiling

Hangzhou Reliability Instrument Corp., Hangzhou, China

Contract Employee (2002)

# MCS-51/98 Microcontroller design and MPU programming.

# Automatic aging testing system for relays and thyristors.

** SELECTED PATENTS & PUBLICATIONS **

Patents (4 out of 8):

1. Tunable hot carrier photodetector, A. G. U. Perera and Y. F. Lao, U. S. Patent Application submitted to the US Patent and Trademark Office, September 3, 2013.

2. Vertical-cavity surface-emitting laser using InAsP/InGaAsP quantum wells and fabrication method, Y. F. Lao, C. F. Cao, H. Z. Wu, C. Liu, M. Cao, SIMIT, CN 200*********, March 2010.

3. Direct wafer-bonding method for integrating indium phosphide and gallium arsenide based materials, H. Z. Wu, Y. F. Lao, Y. S. Hao, SIMIT, CN 200*********, March 2005.

4. Metal-insulator-semiconductor structure using magnesium zinc oxide and its processing technology, H. Z. Wu, J. Liang, Y. F. Lao, SIMIT, CN 03151098, March 2005.

Publications (10 out of 67):

1. Y. F. Lao, A. G. Unil Perera, L. H. Li, S. P. Khanna, E. H. Linfield, and H. C. Liu, Tunable hot-carrier photodetection beyond the bandgap spectral limit, Nature Photonics 8, 412 (2014).

2. Y. F. Lao, et al., Wavelength-extended photovoltaic infrared photodetectors, Appl. Phys. Lett. 104, 131101 (2014).

3. Y.-F. Lao, et al., InAs/GaAs p-type quantum dot infrared photodetector with higher efficiency, Appl. Phys. Lett. 103, 241115 (2013).

4. Y.-F. Lao, et al., Direct observation of spin-orbit splitting and phonon-assisted optical transitions in the valence band by internal photoemission spectroscopy, Physical Review B (Rapid Communications) 88, 201302(R) (2013).

5. Y.-F. Lao, et. al., Band offsets and carrier dynamics of type-II InAs/GaSb superlattice photodetectors studied by internal photoemission spectroscopy, Appl. Phys. Lett. 103, 181110 (2013).

6. Y.-F. Lao, and A. G. Unil Perera, Temperature-dependent internal-photoemission probe for band parameters, Phys. Rev. B. 86, 195315 (2012).

7. S. G. Li, Q. Gong, Y. F. Lao, et al., Two-color quantum dot laser, Appl. Phys. Lett. 95, 251111 (2009).

8. Y.-F. Lao, et al., InAsP/InGaAsP quantum-well 1.3 μCSELs, Electron. Lett. 45, 105 (2009).

9. Y.-F. Lao, et al., Submilliamp Threshold 1.3 μ VCSEL, Acta Physica Sinica 58, 1954 (2009).

10. S. G. Li, Q. Gong,Y. F. Lao, et al., Room temperature continuous-wave operation of InAs/InP quantum dot lasers grown by GSMBE, Appl. Phys. Lett. 93, 111109 (2008).

** EDUCATION **

Ph.D., Microelectronics and Solid State Electronics, Shanghai Institute of Microsystem and Information Technology

M.Sc., Condensed Matter Physics, Zhejiang University

B.Sc., Physics, Zhejiang University; Physics

Full list of patents and publications provided upon request.

REFERENCES FURNISHED UPON REQUEST

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