Self-powered ultraviolet photodetectors based on sub-100-nm nonstoichiometric β-Ga₂O3−δ thin films: role of oxygen vacancies in carrier transport

We report on the performance of ultraviolet (UV) photodetectors based on nonstoichiometric β-Ga 2 O 3−δ thin films with a thickness of 65 nm. The epitaxial Ga 2 O 3−δ films were deposited on sapphire(0001) substrates by radio-frequency powder sputtering at 500 ℃. The oxygen-deficient, nonstoichiometric nature of the films was confirmed by hard X-ray photoelectron spectroscopy. The fabricated metal–semiconductor–metal photodetectors exhibited a photo-to-dark-current ratio of 2.17 × 10 2 , photoresponsivity of 136.15 A/W, and specific detectivity of 5.06 × 10 13 Jones at 10 V under 254 nm UV illumination. Self-powered operation was achieved, yielding a photocurrent of ~0.6 nA at a nominal zero bias. Biexponential fitting of the time-resolved response revealed slow decay components attributed to oxygen-vacancy-related traps. These results indicate that the oxygen vacancies play a dual role by enhancing the photocurrent through free-carrier generation and contributing to persistent photoconductivity. Our findings demonstrate promising potential of sub-100-nm nonstoichiometric β-Ga 2 O 3−δ thin films for high-performance UV photodetectors.