Distinct Short Circuit Capability of 650-V p-GaN Gate HEMTs under Single and Repetitive Tests

Single-event and repetitive short circuit (SC) capability of 650-V Schottky-type p-GaN gate high-electron-mobility transistors (HEMTs) is investigated. The devices exhibit long withstand time $(673 \mu \mathrm{s})$ in a single SC test, but significantly shorter withstand time $(\lt 1 \mu \mathrm{s})$ under repetitive SC tests, with a bus voltage of 400 V and a gate drive voltage of 6 V. Due to the high junction temperature and the dynamic threshold voltage shift, the drain current tends to experience a dramatic drop during the SC transient, resulting in the long SC withstand time. The failure mechanism under repetitive SC tests is revealed through electrothermal simulation and failure spot analysis. Physical cracks are formed due to the high temperature spike and local temperature fluctuations in the GaN channel and buffer layers in the repetitive tests. The temperature spike is attributed to the ultra-high heat generation rate in the thin channel and the heat confinement effect in the GaN channel and buffer layers.