GaN-based HEMT devices for power switching applications

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 V_DS=100V and reverse Schottky-gate leakage current of 2.93μA at V_GD= -100V. After SiN_x passivation, both leakage currents increase nearly one order of magnitude, which are 19.5μA and 14.34μA respectively. On the one hand, the SiN_x 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.