Gate Reliability of Schottky-Type p-GaN Gate HEMTs Under AC Positive Gate Bias Stress With a Switching Drain Bias

With a switching drain bias, the gate reliability of Schottky-type p-GaN gate high-electron-mobility transistors (HEMTs) under AC positive gate bias stress has been systematically investigated. The mean-time-to-failure (MTTF) under such application-relevant stress is found to be prolonged compared to that extracted from static and AC gate bias stress tests with the absence of a switching drain bias and exhibits positive coefficients with frequency and OFF-state drain bias (V-DSQ). Such results can be explained by the drain-induced hole insufficiency in the gate stack at large V-DSQ, a physical mechanism that results in elevated energy band at ON-state when V-DSQ is just switched to low voltage. This non-equilibrium transient status could suppress injection of electrons from the 2DEG channel to thep-GaN gate, which in turn substantiallyweakens the hot-electron's generation in the depleted p-GaN layer and the subsequent bombardment to the gate-metal/p- GaN interface, and thus prolongs the gate lifetime.