Time-dependent gate breakdown of Schottky p-GaN gate HEMTs down to 15 K

This work reveals the role of electron mean free path (λL) in time-dependent gate breakdown (TDGB) of Schottky p-GaN gate through cryogenic temperature measurements down to 15 K. Contrary to the monotonic temperature dependence commonly observed at high temperatures, the temperature dependence of mean time-to-failure and predicted gate lifetime exhibits a distinct transition below 200 K. Specifically, the TDGB lifetime decreases from 300 to 200 K but remains almost unchanged from 200 to 15 K. The dual-mode temperature dependence is attributed to the change of electron energy. The electron energy increases from 300 to 200 K as λL increases, but saturates from 200 to 15 K as λL becomes longer than the depletion width (WD) of the Schottky junction.