Unique Role of Hot-Electron Induced Self-Heating in Determining Gate-Stack Dependent Dynamic RON of AlGaN/GaN HEMTs Under Semi-on State

In this work, we report a unique dependence of dynamic RON on gate-stack of AlGaN/GaN high electron mobility transistors (HEMTs) on carbon (C)-doped GaN buffer under semi-on condition. Unlike the OFF-state stress, semi- ON state stressing of the devices revealed a significantly lower dynamic RON in the Schottky HEMTs when compared to SiNx-gated HEMTs. Detailed experiments including substrate bias dependence, electro-luminescence (EL) spectrum, and electric field analysis established electron trapping in the GaN buffer to be the source of dynamic RON in both the HEMT types. An on-the-fly thermal analysis, using thermoreflectance technique, revealed Schottky HEMTs to have a higher hot electron-induced self-heating near the field plate (FP) edge as compared to SiNx-gated devices. The higher lattice temperature was found to result in a significantly higher electron de-trapping from the buffer traps. The higher de-trapping reduced the dynamic RON in the Schottky HEMTs as compared the SiNx-gated devices.