Separate investigation of performance degradation for the Si and GaN parts in cascode GaN devices under repetitive short circuits

Abstract

In this paper, the performance degradation under repetitive short circuits was investigated for the Si and GaN separately in cascode GaN devices. Self-sustained oscillation is a main obstacle in deeper studying the short-circuit characteristics of cascode GaN devices, in many cases, the device is damaged by the self-sustained oscillations rather than the thermal/electrical stress of short circuits. To avoid the self-sustained oscillations during short circuits, a modified short-circuit test platform is proposed to conduct the short-circuit test safely. To characterize the static performance of the Si and GaN parts separately in a fair way, a new decapsulation method without affecting the die performance is proposed on a commercial cascode GaN device. Considering the trap effect on GaN devices, a fair test procedure is designed to avoid the influence brought by the fluctuation of the GaN threshold voltage. In the end, the performance degradation is analysed after going through repetitive short-circuit tests under 100 V/10 μs. The results show that the on-state resistance increases after short circuits, the Si part is responsible for 38 % in it and the GaN part is responsible for 62 % in it. The threshold of Si part is not changed while the threshold of GaN part increases.