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

Abstract

We report on the performance of ultraviolet (UV) photodetectors based on nonstoichiometric β-Ga<inf>2</inf>O<inf>3−δ</inf> thin films with a thickness of 65 nm. The epitaxial Ga<inf>2</inf>O<inf>3−δ</inf> 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 × 102, photoresponsivity of 136.15 A W−1, and specific detectivity of 5.06 × 1013 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<inf>2</inf>O<inf>3−δ</inf> thin films for high-performance UV photodetectors. © 2025 Elsevier B.V., All rights reserved.