15 MeV proton damage in NiO/β-Ga₂O₃vertical rectifiers

Abstract

15 MeV proton irradiation of vertical geometry NiO/βGa2O3 heterojunction rectifiers produced reductions in reverse breakdown voltage from 4.3 kV to 3.7 kV for a fluence of 1013 cm-2 and 1.93 kV for 1014 cm2. The forward current density was also decreased by 1-2 orders of magnitude under these conditions, with associated increase in on-state resistance RON. 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 x1016 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.

Forward bias annealing of proton radiation damage in NiO/Ga2O3 rectifiers

“…This was also observed in previous studies [63]. It is important to point out that conventional thermal annealing ,ust be carried out at temperatures of at least 300 °C-400 °C in order to observe significant reduxtion in the damage for similar fluence and energies to the conditions eompluyed in this work [36]. The temperatuire of devices in our experiments did not rise above ∼50 °C during carrier injection, so thermal damage is not present.…”

“…While shielding or turning off the devices if it is known that a radiation event will occur are some of the methods employed for reducing the effects of radiation damage, at a device level, various types of annealing may be possible. For example, in similar NiO/Ga 2 O 3 rectifiers to those studied here, annealing at 400 °C was partially successful in restoring the initial properties [36]. While the reverse leakage increased due to reaction of the contacts, the forward current and the initial carrier density in the drift region were significantly restored by this thermal annealing [36].…”

“…For example, in similar NiO/Ga 2 O 3 rectifiers to those studied here, annealing at 400 °C was partially successful in restoring the initial properties [36]. While the reverse leakage increased due to reaction of the contacts, the forward current and the initial carrier density in the drift region were significantly restored by this thermal annealing [36].…”

“…The spread in literature values reflects the dependence of the carrier removal rate on the type of compensating impurities and pre-existing defects, as well as the startingelectron density in the drift region. At high fluences, the electron removal rate will saturate due to the fact all the carriers are trapped and additional introduction of defect states will not affect the electron density [36].…”

“…A schematic representation of the device structure is provided in figure 1. More details are given in reference [36].…”