Degradation mechanisms of AlGaN/GaN HEMTs on sapphire, Si, and SiC substrates under proton irradiation

The degradation mechanisms of AlGaN/GaN high electron mobility transistors (HEMTs) grown on sapphire, Si, and SiC substrates, under 2 MeV proton irradiation are investigated. It was determined by electron channeling contrast imaging that the threading dislocation density of the AlGaN/GaN epitaxial layers is highest on sapphire substrates and lowest on SiC substrates. Photoluminescence spectroscopy confirmed the material quality order from worst to best to be AlGaN/GaN grown on sapphire, Si, and SiC substrates, respectively. The radiation response of sheet carrier density was not statistically different for HEMTs on each substrate, however the mobility degraded more for HEMTs with less initial dislocations (on SiC) than more defective HEMTs (on sapphire).