Thermally activated defect suppression in neutron-irradiated β-Ga₂O₃: from damage tolerance to active defect mitigation

Abstract

Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, is a promising platform for next-generation nuclear sensors in extreme environments. However, a key challenge remains: can radiation-induced damage be intrinsically mitigated during operation rather than passively tolerated? The interplay between defect formation and thermally activated recovery remains poorly understood, limiting predictive design of radiation-hardened devices. Here, we investigate defect evolution in β-Ga₂O₃ under neutron irradiation using the North Carolina State University PULSTAR reactor. Single-crystal samples were irradiated up to ~10¹⁸cm⁻² at room temperature and 700°C using custom vertical ports enabling controlled, dose-dependent retrieval. This capability allows direct observation of defect dynamics under reactor-relevant conditions. Optical transmittance and positron annihilation spectroscopy reveal pronounced defect accumulation and radiation darkening at room temperature, while high-temperature irradiation suppresses stable defect formation. These results demonstrate a thermally activated defect mitigation regime, providing key insights for radiation-resilient Ga₂O₃ devices.