DC and RF Performance of AlGaN/GaN/SiC MOSHEMTs With Deep Sub-Micron T-Gates and Atomic Layer Epitaxy MgCaO as Gate Dielectric

In this letter, we report on the dc and RF performance of AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOSHEMTs) with various gate lengths (LG) from 90 to 500 nm using atomic-layer-epitaxy single crystalline Mg0.25Ca0.75O as gate dielectric. The 90-nm T-gate MOSHEMT simultaneously demonstrates a ft/fmaxof 113/160 GHz with high on/off ratio of5× 10⁸. The on/off ratio increases to2× 10¹¹atLG=350nm by reducing short channel effects. The gate leakage current is around 10−11A/mm at off-state and 10−5A/mm at on-state. A 160 nmLGMOSHEMT also exhibits an output power density of 4.18 W/mm atf = 35GHz andVDS=20V. MgCaO demonstrates to be a promising dielectric for GaN MOS technology in serving as the surface passivation layer and reducing the gate leakage current while maintaining high RF performances for high-power applications.