Title: II-VI and III-V semiconductor integration and their applications in solar cells and other optoelectronic devices

Speaker: Prof. Yong-Hang Zhang (Director of ASU NanoFab and Center for Photonics Innovation, School of Electrical, Computer and Energy Engineering, Arizona State University, USA）

Time: Sept. 23, 2016 10:00AM

Venue: No. 101 meeting room of the library, IOS, CAS

Abstract:Semiconductor optoelectronic materials and devices have experienced very rapid development for more than half a century. However, there still remains a lack of closely lattice-matched materials and substrates suitable for the grand integration of variouskinds of semiconductor optoelectronicand electronic devices on a single chip.I have recently proposed a new material platform: II-VI (MgZnCdHg)(SeTe) and III-V (AlGaIn)(PAsSb) semiconductor materials lattice-matched to GaSb, InAs and InSb substrates. These materials have direct bandgaps covering a very broadenergy spectrum from far IR (~0 eV) to UV (~3.4eV). This feature is not achievable by any other known lattice-matched semiconductors on any commercially available substrates. Such a unique material platform offer opportunities to study new physics such topological insulation in heterovalent superlattice and enablesnewlight emitting devices, multi-junction solar cells, multi-color photodetectors, resonant tunneling diodes, and facilitates monolithic integrationof various materials without misfit dislocations to ensure the best quality for device applications. This talk will focus on the latest progress of the MBE growth of CdTe/MgCdTe heterostructures on InSb substrates. Record interface recombination velocity (~1 cm/s) and ultra-long lifetime (3.6 μs) have been observed, and their applications inCdTe single crystalline solar cells with record high efficiency, andphotodetectors and possibly midwave IR VCSELs will also be presented. At the end, I will briefly mention the potential of the plat for studying various heterovalent superlattice like CdTe/InSb, which may possess novel properties like topological insulator states at the interfaces.

References:

1. Y. Zhao, M. Boccard, S. Liu, J. Becker, X.-H. Zhao, C. M. Campbell, E. Suarez, M. B. Lassise, Z. Holman, and Y.-H. Zhang, Monocrystalline CdTe Solar Cells with Open-Circuit Voltage Over 1V and Efficiency of 17%, Nature Energy 1, 16067 (2016)

2. S. Liu, X.-H. Zhao, C. M. Campbell, M. B. Lassise, Y. Zhao, Y.-H. Zhang, Carrier lifetimes and interface recombination velocities in CdTe/MgxCd1-xTe double heterostructures with different Mg compositions grown by molecular beam epitaxy, Appl. Phys. Letts. 107, 041120 (2015)

Biography：Professor Zhang received his BS from Nanjing Normal University in 1982 and MS from the Institute of Semiconductor in 1987 and did his research at the Max Planck Institute for Solid States andreceived this doctoral degree in physics from the University of Stuttgart in 1991. He then worked as an Assistant Research Engineer at UCSB before he joined Hughes Research Labs in 1993. In 1996, he was appointed Associate Professor in the Department of Electrical Engineering at ASU and was then promoted to full professor in 2000. He edited 3 books, published 3 book chapters and more than 290 peered reviewed papers, presented 388 invited and contributed talks, 12 issued US patents, and advised over 30 PhD students and supervised over 40 postdocs and visiting scholars. He is a fellow of IEEE and OSA, andserved as the Associate Dean for Research at the Fulton Schools of Engineering, and is the founding director of the Center for Photonics Innovation, and the director of a university user facility ASUNanoFab. His areas of research interest include MBE growth, optical properties of semiconductor heterostructures, optoelectronic devices, solar cells, and their applications.More information about his group can be found on the webpage:http://asumbe.eas.asu.edu/. Email: yhzhang@asu.edu.