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) beta-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 x 10(14) cm(-2) and 1.7 x 10(15) 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 similar to 4.8 eV bandgap with high energy resolution, three specific trap states were introduced by neutron irradiation at E-C-1.22 eV, E-C-2.00 eV, and E-C-0.78 eV. Of these, the former two states, observed by DLOS, were also present prior to irradiation, whereas the trap at E-C-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 E-C-2.00 eV appearing as the strongest compensating defect for the neutron-irradiated beta-Ga2O3. (c) 2019 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).