GaN HEMT with p-Type Schottky Gate: A Case Study of TCAD Modeling of the Gate Leakage Current

A normally-off p-GaN gate HEMT for power applications is studied by technology computer-aided design (TCAD) simulations with the aim of showing the key contributions to the gate current. The specific role of physical models, already identified in the literature, are investigated along with the 1D and 2D geometry of the gate region in order to fully understand their correlated effects on device operation. Simple 1D simulations have been carried out to highlight the contributions of band-to-band electron barrier tunneling at the Schottky junction and trap-assisted tunneling through the AlGaN barrier over a fully extended positive gate-bias range. The latter models have been included in 2D simulations accounting for the realistic geometry of the p-GaN edges and the rounding of gate-metal corners. The tunneling at the metal-GaN interface has been monitored by splitting the gate contact into planar and corner portions in the TCAD deck. From the obtained results, a clear and significant edge-current contribution was found, highlighting the relevant role played by the 2D geometry.