Investigating Forward Gate ESD Mechanism of Schottky-type p-GaN Gate HEMTs Using a SiC-based High-Speed Pulsed I-V Test System

The forward gate human-body-model (HBM) electrostatic discharge (ESD) robustness and mechanisms of the Schottky-type p-GaN gate HEMTs are investigated. Unexpectedly, the transient forward gate leakage current ( I G ) is high during appreciable, yet non-destructive, discharge events. To characterize the elevated I G more comprehensively, we use SiC MOSFETs to devise a new pulsed I-V test system. This system is capable of generating voltage pulses with a rise time of ≤ 10 ns and width of < 100 ns, and a maximum pulse current of 26 A. The pulsed I G - V G (gate voltage) characteristics' temperature and time dependencies suggest that the high transient I G is primarily governed by electron thermionic emission across the AlGaN barrier. This emission is stimulated by the dynamic capacitive V G division within the two back-to-back junctions of the p-GaN gate stack rather than by the resistive V G division observed in the steady-state conditions.