108 / 11 / 12 (二) 16:00-17:00
講者： Prof. Shyh-Chiang Shen / School of Electrical and Computer Engineering Georgia Institute of Technology
講題： Development of III-N Power Rectifier and Transistor Switches
摘要：The successful development of III-V nitride materials systems has led to active research of electronic devices in a wide range of system-level applications. III-nitride (III-N)-based devices have a bandgap engineering flexibility, large energy gap, direct band structure, and high carrier mobility when compared to Si- and SiC -based devices, providing new performance improvement opportunities for high-speed radio-frequency (RF) integrated circuits and energy-efficient electronics. Today, GaN HFETs have been extensively studied and commercially off-the-shelf (COTS) components are available. On the other hand, the development of bipolar devices such as rectifiers, transistors and the related switch technologies has yet been fully exploited in III-N materials systems. For instance, a successful development of insulated-gate-bipolar transistors would require material-specific knowledge and well-developed fabrication technologies related to the bipolar transistors and unipolar transistors in a vertically current conduction form. These device technologies are still in an early development stage. III-N bipolar switches in either two-terminal or three-terminal forms are actively sought.
In this presentation, an introductory discussion of the current transistor technology development in GaN materials systems will be provided, followed by a discussion on the development of III-N bipolar switches at Georgia Tech. We will use GaN rectifiers as a case study to discuss the device performance pertinent to the choices of GaN substrates as well as device design and fabrication engineering considerations. Homojunction GaN PIN rectifiers were grown on a 2-inch bulk GaN substrate using a metal-organic chemical vapor deposition (MOCVD) reactor. The fabricated GaN rectifiers showed uniform Von of 3.6±0.1 V, blocking voltage of >1.2 kV, and a specific on-state resistance of < 0.4 mW·cm2. High current drive (>10A) rectifiers with a BV of 1.2kV was achieved. For the development of III-N heterojunction bipolar transistors (HBTs), we have demonstrated world-leading transistor characteristics with a common-emitter current gain of >100, high current drive density of >100 kA/cm2, high d.c. power handling capability of > 3 MW/cm2, and a cut-off frequency (fT) of 8GHz using an InGaN/GaN HBT platform. A preliminary III-nitride pnpn switch performance was also evaluated experimentally. These results demonstrated the feasibility of using bipolar carrier transport mechanisms and PN junctions in III-N devices for power amplifications and switching circuits.