Simulation Study of Gate-Drain Leakage Current and Density of Polarization Charge at Heterojunction Interface in GaN HEMTs

Abstract

In previous report, we showed that the source-drain leakage current at off state can be suppressed by thinning the undoped channel layer even if the gate length was reduced to 25 nm in device simulation of AlGaN/GaN HEMT. On the other hand, if the source-drain leakage current can be suppressed, leak current is dominated by the leakage current between the gate and drain. In this report, the source-drain leakage current and the gate-drain leakage current are calculated when drain voltage is until 50 V. When the sufficiently small access resistance is assumed, change of Al composition of barrier has almost no effect in DC characteristics, while the gate-drain leakage is suppressed when Al composition is lower due to lower polarization charge at heterojunction. To use high Schottky barrier height of the gate of AlGaN layer with high Al composition effectively, reduction of the density of polarization charge by using semi-polar-face is proposed.