Hybrid-gate structure designed for high-performance normally-off p-GaN high-electron-mobility transistor

A normally-off hybrid-gate p-GaN high-electron-mobility transistor (HEMT) is presented in this paper. The gate region is designed as a parallel connection between the Schottky-gate and the metal-insulator-semiconductor gate by inserting a dielectric layer under part of the gate metal. Compared to the conventional Schottky-gate p-GaN HEMT, the fabricated hybrid-gate p-GaN HEMT showed a higher threshold voltage of 3.2 V (increases by 167%), and the maximum transconductance is only a slight decrease (reduces by 23%). At the same time, the forward gate leakage current of the hybrid-gate structure is smaller. Furthermore, through simulation, we revealed that the increase in the threshold voltage originated from the delayed full opening of the two-dimensional electron gas. And we also find that the parameters of the gate dielectric layer have a great influence on the performance of the device. The results show that the hybrid-gate structure is a more promising device structure. © 2020 The Japan Society of Applied Physics.