P-GaN Gate HEMTs: a Solution to Improve the High-Temperature Gate Lifetime

In this letter, we report an approach to improve the forward bias gate reliability of Schottky gate p-GaN HEMTs. In particular, a gate layout solution, namely Gate Within Active Area (GWA), aimed at improving the high-temperature time to failure (TTF), is proposed and validated. This solution allows to avoid the exposure of the gate finger (p-GaN/metal) to the nitrogen-implantation needed for termination and isolation purposes. GWA devices feature a significantly improved gate reliability at high temperature with respect to the reference ones, under both DC and pulsed stress tests. Finally, it is demonstrated that the Schottky gate p-GaN HEMTs show a positive temperature-dependent gate TTF in a range up to 150 °C, confirming the crucial role of impact ionization on the gate failure.