Temperature-Dependent Gate Degradation of $p$-GaN Gate HEMTs under Static and Dynamic Positive Gate Stress

This paper experimentally investigates the time-dependent gate degradation of Schottky-type p-GaN gate transistors subjected to positive gate voltage stress. By means of combined static/dynamic gate stress and temperature-dependent analysis, the dependence of time-to-breakdown ( tBD) on stress mode and temperature are unveiled. It is demonstrated that tBD is Weibull distributed and the mean-time-to-failure (MTTF) is comparable under static and dynamic stress conditions. Both the gate breakdown voltage and MTTF exhibit positive temperature dependence. The maximum applicable gate voltage for a 10-year lifetime is extrapolated at different stress conditions. Moreover, the mechanism of the gate degradation is discussed by comparing the devices' performance before and after the progressive breakdown. It is revealed that electrons accelerated in the depletion region of the p-GaN layer under large forward gate bias would gain enough energy and induce defects near the metal/ p-GaN interface, resulting in the time-dependent gate degradation.