Radiation damage and hardening via supercritical fluid process in Al₂O₃/β-Ga₂O₃ MOSCAPs: Insights from proton, Ta-ion, γ-ray, and neutron irradiation

β-Ga₂O₃ devices hold great promise for applications in space environments, yet their electrical performance degrades under particle and ray irradiation in a distinct manner. This study systematically compared the distinct irradiation effects of proton, tantalum (Ta)-ion, γ-ray, and neutron irradiation on Al₂O₃/β-Ga₂O₃ metal–oxide–semiconductor capacitors (MOSCAPs) and validated low-temperature supercritical fluid pretreatment for radiation hardening by suppressing ionization damage. Electrical measurements were employed to investigate the influence of variations in border traps in the Al₂O₃ layer, heterojunction interface traps, and net carrier concentration in β-Ga₂O₃ on the device performance. The results revealed that the coupling and competition among ionization damage, displacement damage, and localized annealing effects collectively governed the different degradation behaviors. Specifically, the increase in border traps and interface traps induced by displacement damage and ionization damage led to increased leakage current and reduced breakdown electric field (E _br). Moreover, Ta-ion irradiation-induced localized annealing and neutron irradiation-induced excessive carrier removal could partially mitigate irradiation damage, with the former improving the quality of Al₂O₃ layer and the latter increasing E _br. Based on the analysis of irradiation damage mechanisms, pre-passivation of intrinsic defects in Al₂O₃ effectively enhanced γ-ray irradiation resistance of the MOSCAPs, offering a new strategy for the radiation-hardening design of β-Ga₂O₃ devices with Al₂O₃/β-Ga₂O₃ MOS structures.