Multimodal optical positron characterization of radiation-induced defects and their evolution in β-Ga2O3

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Abstract
Gallium oxide (Ga 2 O 3 ) is an emerging candidate for next-generation radiation detectors due to its ultrawide bandgap, high-temperature stability, and large breakdown field, making its radiation tolerance and defect behavior critical to advancing device performance. To investigate the mechanisms of radiation damage and microstructural evolution, β-Ga 2 O 3 samples were irradiated at the North Carolina State University PULSTAR reactor to neutron fluences up to ~10 18 cm −2 at both room temperature and 700 °C using custom vertical irradiation ports that enable continuous exposure while allowing selective retrieval of samples at predetermined dose levels. Post-irradiation characterization using optical transmittance measurements and positron annihilation spectroscopy (PAS) revealed pronounced radiation darkening and reduced transmittance in room-temperature-irradiated samples, accompanied by increased positron lifetimes indicative of progressive defect accumulation. In contrast, samples irradiated at 700 °C exhibited minimal optical darkening and negligible changes in positron lifetime, suggesting that elevated temperature suppresses the formation or retention of neutron-induced defects. These results highlight a thermal threshold that strongly governs defect diffusion, recombination, and trapping behavior in β-Ga 2 O 3 , providing insight into pathways for enhancing its radiation resilience for nuclear and high-energy applications.
Funding Information
  • Nuclear Energy University Program (DE-NE0009192)
  • Idaho Operations Office, U.S. Department of Energy (CCN:253882)

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