III-Nitride (III-N) transistors offer tremendous performance advantages when compared to silicon-based power electronic components. These advantages include ultra-high powerdensity handling, high short switching transients. This presentation will discuss recent progress in two key III-N transistor technologies: highvoltage AlGaN/GaN heterojunction field-effect transistors (HFETs) and GaN/InGaN RF heterojunction bipolar transistor (HBTs). While III-N HEFTs are extensively studied for millimeter-wave applications, these transistors also showed great potential to drastically reduce the on-state resistance by at least a factor of 100 when compared to silicon counterparts and to enable power switches built-in an III-N integrated circuit. At Georgia Tech, III-N HFETs built on sapphire substrates achieved a 10-ampere drain current drive with a blocking voltage of 1 kV. Using similar techniques, we also achieved both normally-on and normally-off III-N HFETs using a GaN-on-silicon platform with the blocking voltage greater than 1.4 kV. The reported switching characteristics of III-N FET switches are among the best results reported to date for GaN-on-Si platforms. Another grand challenge in III-N transistor development is the realization of high-performance HBTs. In recent years, III-N HBTs employing GaN/InGaN heterostructures demonstrated significant improvements in the power gain and the microwave performance. In the course of the HBT research, we successfully demonstrated GaN/InGaN HBTs with good current gain (> 100) with low offset voltage (< 0.3 V) and knee voltage (< 2 V). Through these developments, we showed the first microwave operation of III-N HBTs with fT > 5 GHz and a common-emitter breakdown voltage of greater than 100 V. When a native free-standing GaN substrate is used, we also demonstrated higher d.c power handling density with > 7X improvement in the collector current drive when compared to devices on the sapphire substrate platform. The d.c. power handling for InGaN HBTs is rated as high as 3 MW/cm 2 in these devices. At 250 °C, IIIN HBTs also showed good current gain (> 40) and an increase of the breakdown voltage by > 30%, implying the feasibility of these transistors for high-temperature operation. This seminar will discuss the development status, technical issues, and applications of these high-voltage transistors for next-generation power electronics.
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- Dr. Shen is a recipient of the 2000 Gregory E. Stillman Fellowship in ECE at UIUC, the 2001 Gregory E. Stillman Semiconductor Award (ECE, UIUC), the 2010 Richard M. Bass Outstanding Teacher Award (ECE, Georgia Tech), and the 2011 Outstanding Junior Faculty Award (ECE, Georgia Tech). He is an IEEE senior member and has served as a TPC member and session chair of the CSMANTECH conference since 2006.
University of Illinois at Urbana-Champaign