Enhancing the thin-film properties of hetero-epitaxial α-Ga2O3 for scalable deep ultraviolet photodetectors

α-Ga2O3, a wide-bandgap semiconductor, has emerged as a promising material for diverse applications. This study presents a high-performance deep-ultraviolet (DUV) photodetector (PD) based on a hetero-epitaxial α-Ga2O3 thin film with reduced defects. The 200-nm-thick α-Ga2O3 thin film is directly grown on a sapphire substrate without a buffer layer using hydride vapor phase epitaxy. The film exhibited strong absorption exceeding 80% in the DUV region below 280 nm and excellent solar-blind characteristics. Post-growth rapid thermal annealing (RTA) in an oxygen atmosphere reduces the oxygen vacancy concentration from 17% to 12%, effectively eliminating defects and enhancing charge transport and collection. The device subjected to RTA for 5 min exhibits a responsivity of 2.03 A W−1, a detectivity of 6.95 × 1013 Jones, an external quantum efficiency of 1095%, and rise and decay times of 2.352 and 0.266 s, respectively. These values represent significant improvements over those of the unannealed device (1.08 A W−1, 3.32 × 1013 Jones, 583%, and 3.263 and 0.484 s, respectively). These results demonstrate that RTA offers a simple yet effective means of enhancing device performance by controlling defects without altering the device structure, highlighting α-Ga2O3 as a cost-effective platform for high-performance DUV PDs.