(Invited) Breakthrough Avalanche and Short Circuit Robustness in Vertical GaN Power Devices

Abstract

After decades of relentless efforts, GaN power devices, specifically, the lateral GaN high-electron mobility transistor (HEMT), have been commercialized in the 15-650 V classes. Owing to GaN’s competitive physical properties over Si and SiC for power electronics, GaN HEMTs allow for higher switching frequency and therefore, have already seen wide adoptions in fast chargers, wireless charging, data centers, and electrified transportation. Despite the success of lateral GaN HEMTs, a vertical device structure is usually believed to be more favorable for high-voltage, high-power devices. In the last few years, with the advent and maturity of large-diameter, low-dislocation GaN wafers on freestanding GaN substrates, a new generation of vertical GaN power devices have been developed to extend GaN’s application space beyond 650 V. Very recently, several industrial vertical GaN devices in the voltage classes of 1.2-1.7 kV have been demonstrated, which are close to commercialization.This presentation will review the key advancements in vertical GaN power devices in the past decade, with a focus on the device technologies that are being commercialized, and provide a prospective for research and development in the next decade. The devices to be covered will include two-terminal power rectifiers including the p-n diodes, Schottky barrier diodes, junction barrier Schottky diodes, and trench MIS/MOS barrier Schottky diodes. The transistors will include the trench and planar MOSFETs, current-aperture vertical electron transistors, fin-channel MOSFETs, and fin-channel JFETs. Particular emphasis will be on large-area rectifiers and transistors with a device performance superior to similarly-rated Si and SiC transistors. The newly demonstrated avalanche and short-circuit robustness in vertical GaN devices, which are lacking in lateral GaN HEMTs, as well as their underlying device physics, will also be introduced. The presentation will be concluded by a discussion of current challenges and future application spaces of vertical GaN devices, as well as emerging vertical GaN devices (e.g., superjunction) under development.