15 MeV proton damage in NiO/ β-Ga₂O₃vertical rectifiers

15 MeV proton irradiation of vertical geometry NiO/β-Ga2O3 heterojunction rectifiers produced reductions in reverse breakdown voltage from 4.3 kV to 3.7 kV for a fluence of 1013ions·cm-2 and 1.93 kV for 1014 ions·cm-2. The forward current density was also decreased by 1-2 orders of magnitude under these conditions, with associated increase in on-state resistance R ON. These changes are due to a reduction in carrier density and mobility in the drift region. The reverse leakage current increased by a factor of ∼2 for the higher fluence. Subsequent annealing up to 400 °C further increased reverse leakage due to deterioration of the contacts, but the initial carrier density of 2.2 × 1016 cm-3 was almost fully restored by this annealing in the lower fluence samples and by more than 50% in the 1014 cm-2 irradiated devices. Carrier removal rates in the Ga2O3 were in the range 190-1200 for the fluence range employed, similar to Schottky rectifiers without the NiO.