High-performance normally off AlGaN/GaN-on-Si HEMTs with partially recessed SiN<i> _x </i> MIS structure

Abstract

Recessed MIS gate structures with SiNx gate dielectric layer were investigated for use in normally off AlGaN/GaN-on-Si high electron mobility transistors (HEMTs). The channel mobility and threshold voltage (Vth) instability were strongly affected by the recessed configuration. Employing a 30 nm SiNx gate dielectric layer composed of 6 nm PEALD and 24 nm ICP-CVD films on a 2 nm AlGaN recessed barrier layer resulted in excellent electrical and dynamic characteristics with reduced effective interface trap density. A maximum drain current density of 590 mA mm−1, an on-resistance of 0.75 mΩ · cm2, and a breakdown voltage of >1100 V were achieved for the gate-to-drain distance of 10 μm. Owing to the remaining AlGaN barrier layer under the recessed gate region of the partially recessed device, the interaction between MIS interface traps and channel electrons was suppressed effectively, resulting in improved channel mobility and Vth stability.