Analysis of MOCVD SiNx Passivated N-Polar GaN MIS-HEMTs on Sapphire With High $f_{max}\cdot V_{DS,Q}$

Abstract

This letter presents an analysis of N-polar metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with a 40 nm MOCVD SiNx passivation and a trench-gate design. A device with a 50 nm gate-length ( L g ) demonstrates a 313 GHz power gain cutoff frequency ( f max ) at a quiescent drain bias ( V $_{{DS,Q}}$ ) of 26 V. The high $f_{max}\cdot V_{DS,Q}$ of 8.1 THz $\cdot$ V exhibits great potential of the device in high-frequency power applications. Investigation on small-signal parameters shows that f max improves with V $_{{DS,Q}}$ due to a reduction of gate-drain capacitance ( c gd ) and an increase of output resistance ( rds ). When comparing with the previously reported planar HEMT design, the shorter L g enabled by the trench-gate design enhances the intrinsic current gain cutoff frequency ( f $_{{T,int}}$ ) leading to a higher peak f max at a higher V $_{{DS,Q}}$ .