Suppression of Gate Leakage Current in Ka-Band AlGaN/GaN HEMT With 5-nm SiN Gate Dielectric Grown by Plasma-Enhanced ALD

A Ka-band AlGaN/GaN metal-insulator- semiconductor high-electron-mobility transistor (MISHEMT) with SiN gate dielectric grown by plasma-enhanced atomic layer deposition (PEALD) is demonstrated. The gate reverse leakage current in a controlled HEMT is reduced by about three orders of magnitude by the PEALD-SiN, contributing to an improved breakdown voltage of 92.5 V (source-drain separation of 2.0 μm) in the fabricated MIS-HEMTs. The MIS-HEMTs also feature small threshold voltage hysteresis in dc transfer and capacitance-voltage characterizations, suggesting a good PEALD-SiN/AlGaN interface. The fabricated MIS-HEMTs deliver a high output power density of 7.16 W/mm and a peak power-added efficiency of 60.3%, respectively, at V
_DS
= 30 V and V
_DS
= 10 V in pulse mode at 28 GHz. PEALD-SiN could be a compelling gate dielectric for fabrication of high-power and high-efficiency MIS-HEMTs.