Accelerating the Recovery of p-Gate GaN HEMTs after Overvoltage Stresses

Abstract

GaN high electron mobility transistors (HEMTs) have limited avalanche capability and withstand the surge energy through capacitive charging, which often causes significant voltage overshoot up to their catastrophic limit. This work explores the parametric shift and recovery of a commercial Schottky-type, p-gate GaN HEMT under repetitive, overvoltage switching stresses near its dynamic breakdown voltage. In particular, the device recovery under various temperatures is comprehensively studied, which allows the identification of the de-trapping dynamics and dominant trap energy levels for the first time. Devices were stressed in a clamped inductive switching circuit with 1-million surge energy cycles with a voltage overshoot reaching 1300 V. The parametric shifts showed a saturation and were found to be caused by holes generated in impact ionization. The device recovery was found to be accelerated by elevated ambient temperatures, and a hole-trap energy level of 0.52 eV was identified to dominate the parametric shift and recovery. These results suggest the significance of hole dynamics on the overvoltage robustness of p-gate GaN HEMTs near their dynamic breakdown voltage.