Swift heavy ion irradiation-driven energy band engineering and its profound influence on the photoresponse of -Ga₂O₃ ultraviolet photodetectors

Swift heavy Ta ions with an ultra-high energy of 2896 MeV are utilized for irradiation of beta-Ga2O3 photodetectors. Noteworthy variations in device performance under different wavelengths are observed. Under 254 nm light illumination, the photocurrent of the devices exhibit degradation at low ion fluences but gradually recover and even surpass the performance of non-irradiated devices at the irradiation fluence of 1 x 10(10) cm(-2). Conversely, under 365 nm light illumination, photocurrent increases at low fluence but slightly decreases at the same high fluence of 1 x 10(10) cm(-2). Cathodoluminescence spectra and first-principles calculations elucidate the mechanism underlying the evolution of device performance with irradiation fluence. At low irradiation fluence, the introduction of point defects such as oxygen vacancies and gallium vacancies leads to an expansion of the bandgap, resulting in a decline in photocurrent under 254 nm light illumination. Additionally, deep defect levels are generated by these point defects, promoting an enhancement of photocurrent under 365 nm light illumination. Higher fluences transform these point defects into complex defects such as Ga-O pair vacancies, resulting in a reduction in the bandgap. Consequently, an increase in photocurrent is observed for devices illuminated with 254 nm light. However, at high irradiation fluences, charge recombination induced by the presence of deep defect levels becomes more significant, leading to a decrease in photocurrent when exposed to 365 nm light. No matter what, at 1 x 10(10) cm(-2) fluence, beta-Ga2O3 photodetectors still maintain excellent performance, implying their strong radiation resistance and immense potential for application in space environments.