Center for Functional Nanomaterials Seminar

Semiconductor infrared photodetectors are widely used in optical communications, optical sensing, thermal imaging, and many other applications. Recently, there is a new demand for high-power high-speed photodetectors in microwave photonic systems, such as optically steered phased array radars. In these systems, very high power optical input is used to increase the system dynamic range and to convert to a high power electric output to drive a heavy load such as an antenna. Another active research area is using avalanche photodetectors as a single-photon counter. It attracted more and more research effort because of various sensing and quantum information processing applications. I will talk about my work on developing a new photodetector structure with undepleted absorption region for both high optical input power and single-photon counting applications. Several methods used to increase the photodetector responsivity using resonant-cavity and waveguide structures will also be discussed. Metal-oxide-semiconductor field-effect-transistor (MOSFET) is the basic building block of Integrated Circuits (ICs). The rapid growth of IC industry was based on the continuous scaling down of silicon MOSFETs. As further scaling becomes unrealistic in the near future, using high mobility III-V channel materials emerged as an attractive solution. Among III-V materials, InAs exhibits extraordinarily high electron mobility and saturation drift velocity. The difficulty in growing high surface-quality InAs films hindered the research in this area. Another major issue for all III-V MOS structure is the lack of high-quality insulator-semiconductor interface. I will talk about my recent work growing InAs on lattice-mismatched GaAs substrate using MBE, as well as the results on InAs MOSFETs with Al2O3 gate dielectric. At the end of this presentation, I propose several research ideas on investigating nanomaterials for optoelectronic devices for energy conversion applications.