Influence of neutron irradiation on deep levels in Ge-doped (010) β-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy

The impact of high energy neutron irradiation on the creation of specific radiation-induced deep level defect states and the ensuing influence of these defects on the electronic properties of (010) β-Ga2O3, doped with Ge and grown by plasma-assisted molecular beam epitaxy, were explored. A significant amount of carrier removal was observed in the irradiated samples exposed to 1 MeV equivalent neutron fluences of 8.5 × 1014 cm−2 and 1.7 × 1015 cm−2, which suggests the formation of compensating defects by neutron irradiation. Using a combination of deep level transient/optical spectroscopy (DLTS/DLOS) techniques to probe the entire ∼4.8 eV bandgap with high energy resolution, three specific trap states were introduced by neutron irradiation at EC-1.22 eV, EC-2.00 eV, and EC-0.78 eV. Of these, the former two states, observed by DLOS, were also present prior to irradiation, whereas the trap at EC-0.78 eV, observed by DLTS, was not evident prior to neutron irradiation. The radiation dependence suggests that intrinsic point defects are the likely physical sources for these states. Subsequent lighted capacitance-voltage measurements further revealed that these three states are the source for the observed strong carrier compensation, with the trap at EC-2.00 eV appearing as the strongest compensating defect for the neutron-irradiated β-Ga2O3.