GaN-based HEMT devices for power switching applications

Abstract

GaN-based high electron mobility transistors (HEMTs) have successfully demonstrated unprecedented potential in microwave power electronics applications, featuring both high saturation current and high breakdown voltage. Especially, increasing the gate-drain distance is very beneficial to reduce the off-state leakage current for power switching devices. GaN HEMT devices with the gate-drain distance of 29μm have obtained very low off-state leakage current of 3.8μA at VDS=100V and reverse Schottky-gate leakage current of 2.93μA at VGD= -100V. After SiNx passivation, both leakage currents increase nearly one order of magnitude, which are 19.5μA and 14.34μA respectively. On the one hand, the SiNx dielectric layer decreases surface current leakage and suppresses the virtual-gate effect on the electric-field distribution. On the other hand, it increases the electric-field strength near the gate edge at the drain side, resulting in higher Schottky-gate leakage current. Anyway, GaN HEMT devices show a great potential to achieve breakdown voltage of several hundred volts. Further in combination with field-plate technique, the great reduction of peak electric field at gate edge is advantageous for highvoltage applications.