Step-Stress Reliability Studies on AlGaN/GaN High Electron Mobility Transistors on Silicon with Buffer Thickness Dependence

Off-state bias stress reliability studies were carried out on AlGaN/GaN high-electron-mobility transistors (HEMTs) on Si substrate with different buffer thicknesses. Critical voltage ( V crit ) and preferential electroluminescence (EL) emission were observed for HEMTs grown on 2.5-µm-thick buffer layer, which is believed to be due to nonuniform electric field at the gate–drain region. In contrast, HEMTs with a 4.0-µm-thick buffer layer did not show any sign of V crit , which was further accompanied by a uniform EL emission. This is due to the improved quality of GaN grown on thick buffer layer, which dispels the nonuniform electric field at the gate–drain region.