Early stage degradation related to dislocation evolution in neutron irradiated AlGaN/GaN HEMTs

Abstract

The early stage degradation of electrical properties in AlGaN/GaN high electron mobility transistors (HEMTs) under fast neutron irradiation is studied. After the 1 MeV neutron irradiation at a low fluence of 1 × 1014 neutrons/cm2, the reverse leakage current decreases while the output and transfer characteristics remain unchanged, which cannot be explained by the previously reported high-fluence degradation model. By employing temperature-dependent gate leakage current measurements, we show that the dislocation related Poole–Frenkel (PF) emission dominates the gate leakage mechanism before and after irradiation whereas the barrier height for electron emission to conductive dislocation increases after the neutron irradiation. A model with the evolution of dislocation from the VGa-decorated configuration to the pure configuration is proposed to describe the degradation of AlGaN/GaN HEMTs at the low-fluence early stage neutron irradiation. This model enriches the understanding of the degradation mechanism of neutron irradiated AlGaN/GaN HEMTs.