Perimeter Driven Transport in the p-GaN Gate as a Limiting Factor for Gate Reliability

In this paper, we present an in-depth study of the gate leakage mechanisms and correlated breakdown of GaN-based power HEMTs with p-GaN gate, controlled by a Schottky metal/ p-GaN junction. A detailed investigation of the process split and geometry dependency is done. From this study, we propose that a parasitic sidewall transistor is present, which is the cause for degradation in the p-GaN gate. The sidewall leakage has been substantiated by TCAD simulation and also by a novel method consisting of EBIC measurements directly applied on the cross section of a p-GaN gate. Based on this analysis we performed a process modification, which has led to a significant improvement in terms of gate reliability.