In-depth investigation of low-energy proton irradiation effect on the structural and photoresponse properties of ε-Ga₂O₃ thin films

Ga₂O₃ possesses an ultra-wide bandgap (∼4.9 eV) and an extremely large breakdown field strength (∼8 MV/cm), which promises extraordinary application potential in power electronics and ultraviolet optoelectronics. With the demand for highly durable devices in harsh environments such as in low earth orbit spacecraft, in-depth understanding of the particle radiation effect on the structural and performance degradation of the device is desired. In this work, we employ 150 keV low energy proton with intensity up to 5 × 10¹⁵ dose to irradiate the epitaxial ε-Ga₂O₃ thin films. The characterization of the structural and optical properties shows no detectable variations in lattice structure and optical transmission. In addition, with increasing irradiation dosage, a decrease of Ga³⁺ population and an increase of the concentration of oxygen vacancies are confirmed by X-ray photoemission spectroscopy. Photoresponse measurements further illustrate that, despite of a mild degradation in the photodetector performance, the device still shows a high photoresponsivity of 2.52 × 10^-3 A/W and a large photo-to-dark current ratio over 10³. Our work reveals that ε-Ga₂O₃ exhibits excellent radiation hardness under low-energy proton irradiation conditions and highlights the potential for operational optoelectronics in extreme environment.