High-voltage normally off GaN-based MIS-HEMTs featuring rounded gate sidewalls

This work proposes a normally off gallium nitride (GaN)-based high electron mobility transistor (HEMT) that features rounded gate sidewalls and smooth corner profiles. To facilitate superior gate dielectric growth and coverage, we employed a hybrid-recess scheme combining a two-step etching process with an N2/O2 plasma treatment, resulting in significant etch-induced damage mitigation and interface trap density reduction. Compared to the traditional devices without plasma treatment, our devices exhibited not only a remarkable 156% rise in saturation current density but also a dramatic 108% increase in transconductance, alongside the nearly eliminated threshold-voltage hysteresis. More importantly, attributed to the suppression of the peak electric field under high-voltage stress by the rounded corners, the gate breakdown voltage and off-state breakdown voltage are enhanced to 26 and 1447 V, respectively, consistent with the technology computer-aided design simulation analysis. Finally, double-pulse measurements were conducted to further confirm the reduced interface trap density and improved reliability of the hybrid-recess device. In summary, we demonstrate a normally off GaN-based HEMT with rounded etched sidewalls as a key feature, thereby establishing a promising strategy for high-voltage power devices.