Impact of deep level defects induced by high energy neutron radiation in β-Ga2O3

The effects of high energy neutron irradiation on the deep level defect concentration profile throughout the bandgap of β-Ga2O3 were investigated by a combination of deep level optical spectroscopy (DLOS) and deep level transient spectroscopy (DLTS). For the unintentionally doped edge-defined film-fed growth-grown (010) β-Ga2O3 substrates investigated here, it was found that the dominant effects of neutron irradiation were to produce defects detected by DLOS having energy levels of EC −1.29 eV and EC −2.00 eV, with no discernable impact on traps within ∼1 eV of the conduction band edge. Commensurate with the introduction of these states was a significant amount of net doping reduction, for which lighted capacitance-voltage studies revealed that both of these irradiation-induced deep states are responsible, likely through a compensation mechanism. The sensitivity of the EC −1.29 eV and EC −2.00 eV states on irradiation suggests an intrinsic source, and whereas the EC −2.00 eV state was already present in the as-grown material, the EC −1.29 eV state was not detected prior to irradiation. DLOS and DLTS revealed other defect states at EC −0.63 eV, EC −0.81 eV, and EC −4.48 eV, but none of these responded to neutron irradiation for two different 1 MeV equivalent fluences 8.5 × 1014 cm−2 and 1.7 × 1015 cm−2, which is consistent with the behavior expected for defect states having an extrinsic source.