Solar-blind deep-ultraviolet photodetector based on the β-Ga2O3 thin film grown on annealed c-plane sapphire substrate

p-Ga ₂ O ₃ thin films were epitaxially grown on the as-supplied and vacuum-annealed c-plane sapphire substrates, and the structural and deep-ultraviolet photosensitive properties were investigated. It was found that the vacuum-annealing pretreatment yielded a smoother substrate surface, and thus resulted in a significant improvement in the crystal quality of β-Ga ₂ O ₃ epitaxial film. As a result, both dark and photo currents of P-Ga ₂ O ₃ photodetector were increased. However, the increase extent of photocurrent was relatively small unless the substrate-annealing temperature was high enough. The result can be attributed to three factors compromising each other: carrier mobility, the transitions from valence-band tail to conduction band, and recombination centers. Accordingly, the p-Ga ₂ O ₃ photodetector fabricated on the 1050 °C-annealed substrate exhibited excellent deep-ultraviolet photosensitive properties, for example, a large photocurrent of 3540 nA, a high responsivity of 143.3 A/W, and an outstanding photo-to-dark current ratio of 2.48×10 ⁴ .