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Professor Asif KhanCarolina Distinguished ProfessorUniversity of South Carolina
AbstractUltrawide bandgap (UWBG) AlxGa1-xN (x>0.4) is an ideal material for UVC LEDs and lasers, and high-voltage/power/frequency devices. It has a direct bandgap in the UVB/UVC part of the spectrum and the breakdown voltage, which scales with the bandgap, can reach values between 7-10 MV/cm. One of the challenges in developing UWBG AlGaN device epitaxial structures is the absence of low-cost bulk AlN substrates. This, we have overcome by developing a high-temperature low-pressure MOCVD process which yields very high quality AlN/sapphire templates with AlN layer thicknesses from 4-17 µm. These are an ideal platform for growing the epitaxial UWBG AlGaN layers and heterojunctions for the optical and electronic devices. The UWBG AlGaN layers however pose additional challenges in materials growth, doping and ohmic contact fabrication. In this presentation we will describe the approaches we have adopted to overcome some of these issues. Recent results from our group on UWBG AlGaN channel depletion and enhancement mode high electron mobility transistors (HEMTs) with gate dielectrics will be presented. We will also discuss some of our recent results on the fabrication of high brightness UVC micro-LEDs with pixel sizes below 10 µm diameters.
Professor Khan is a Carolina Distinguished Professor in the department of Electrical Engineering at the University of South Carolina (UofSC). Prior to joining UofSC in 1997, he worked at Honeywell Research Center (1979-1984), Minnesota Manufacturing and Mining Company (3M-1984-1986) and APA Optics (1987-1997).He obtained his PhD from MIT in 1979.
Prof. Khan received the inaugural IEEE Les Eastman Award in 2020, South Carolina Governor’s Award of Excellence in Science and Technology (2015), the best research paper awards of the Japanese Society of Applied Physics (2004 and 2006), DARPA SUVOS Award for UVC LEDs (2003) and is a Fellow of IEEE since 2006. He has published over 420 research papers and hold over 50 US/International patents.
Prof. Khan’s research groups over the years have been pioneers in the development of III-Nitride materials and devices. They were the first to demonstrate all the key building blocks for GaN power and rf-electronics which currently are commercialized by major industries for Electric Vehicles and other control applications. His group at UofSC also was the first to fabricate milliwatt power UVC LEDs. He was a founding member of SETI and Nitek Inc., two South Carolina small businesses which produce and market UVC LEDs.They have now been acquired by Seoul Semiconductor which is a top five global LED manufacturer. More recently Prof. Khan’s group has focused on the development of UWBG AlGaN channel electronics for high-voltage/high-power applications.