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.