Title: Surface Plasmon Enhanced GeSiSn Infrared Detectors
Speaker: Prof. Greg Sun（University of Massachusetts Boston，USA）
Time: OCT. 23, 2015 9:30AM
Venue: No. 320 Meeting Room, Building 3, IOS, CAS
Abstract: Si as a platform for building photonic devices has been challenged by a detrimental intrinsic property of being an indirect bandgap semiconductor. In fact, Si, Ge and their alloys all have an indirect band gap that precludes the fabrication of conventional interband emitters such as LEDs and lasers. The incorporation of another group-IV element Sn into the mix of Si, Ge and their alloy has opened up the possibility of producing Si-based direct bandgap group-IV materials. Recent results have suggested that with sufficient Sn composition the bandgap of the group-IV alloy SiGeSn may indeed become direct and its value can be tailored to be responsive to a wider range of IR spectrum. This collaborative effort has resulted in mid-IR room-temperature electroluminescence from a Ge/Ge0.96Sn0.04/Ge double heterostructure diode and fully strained GeSn-based p-i-n photodiodes, in addition to progress made in growth and characterization of such a material system. Building upon these successes, we are currently working on surface plasmon enhanced GeSn-based mid-IR detectors. Trial fabrications are ongoing based on designs utilizing back illumination and optical absorption properties of the GeSn alloy along with the plasmonic enhancement offered by metal nanostructures. In this talk, I will first provide a brief overview of our group-IV material and device development. I will then discuss the working mechanism of field enhancement by metal nanostructures and the design of several Au nanostructures that are subsequently patterned on GeSn mid-IR detectors. Finally, I will present some preliminary experimental results obtained from fabricated device structures and show enhancement of responsivity measured from these devices.
Biography：Greg Sun received his B.S. in Microelectronics from Peking University in 1984, M.S. in Electrical Engineering from Marquette University in 1988, and Ph.D. in Electrical Engineering from Johns Hopkins University in 1993. Since then, he joined the faculty at the University of Massachusetts Boston as a faculty. Prior to that from 1990 to1992, he worked as a research fellow at Philips Laboratories, Briarcliff Manor, New York, conducting research on ZnSe-based blue lasers. Currently, he is a full professor in Electrical Engineering, and serves as the Director of the Engineering Program at UMass Boston where he is leading the effort to establish the Department of Engineering. His research efforts focus on theoretical investigations in semiconductor optoelectronics and nanophotonics. He has published about 100 papers in refereed journals. He has delivered over 90 invited and contributed conference papers, and given over 30 seminars and colloquia. He serves on various conference committees and on the editorial board of a technical journal.