Substrate-Dependent Effects on the Response of AlGaN/GaN HEMTs to 2-MeV Proton Irradiation

AlGaN/GaN high electron mobility transistors grown on Si, SiC, and sapphire substrates were exposed to 2-MeV proton irradiation in incremental fluences up to 6 × 10¹⁴ cm^-2. The devices were characterized initially and after each irradiation by Hall and dc I-V measurements to probe the mechanisms associated with radiation-induced degradation and failure. It was determined that defects created at the AlGaN/GaN interface introduce scattering centers near the two-dimensional electron gas (2DEG), which result in degraded mobility. Additionally, charged traps in the structure serve to screen the 2DEG resulting in reduced sheet carrier density. These two effects are responsible for degraded I-V behavior, including reduced saturation current and transconductance, increased ON-resistance, and positive threshold voltage shift. Interestingly, the sample with the most pre-existing defects was the most tolerant of radiation-induced damage.