High‐Performance Solar‐Blind Photodetectors Enabled by Post‐Annealing Optimization of Solution‐Processed Ga ₂ O ₃ Films

Gallium oxide (Ga 2 O 3 ) is an ultra‐wide‐bandgap semiconductor with an intrinsic absorption edge in the solar‐blind region, making it attractive for deep‐ultraviolet photodetectors. However, solution‐processed Ga 2 O 3 photodetectors typically exhibit limited photoresponse, which hinders their practical application. Therefore, developing effective post‐annealing strategies to regulate defect states and improve optoelectronic performance is essential. In this work, the post‐annealing process of solution‐processed Ga 2 O 3 films is investigated by tailoring the annealing atmosphere and temperature. By varying the annealing atmosphere using different gas compositions, oxygen‐related defect states are modulated, as revealed by x‐ray photoelectron spectroscopy, leading to enhanced photocurrent and photo‐to‐dark‐current ratio. In addition, the influence of annealing temperature on device performance is evaluated through the evolution of photoresponse characteristics, revealing an optimal thermal treatment window for maximizing photoconductive gain while maintaining low dark current. Through the combined optimization of annealing atmosphere and temperature, Ga 2 O 3 solar‐blind photodetectors with enhanced photoresponse are achieved, exhibiting a responsivity of 7.5 × 10 2 A W −1 under 254 nm illumination together with high external quantum efficiency and specific detectivity. These results demonstrate that controlled post‐annealing optimization provides an effective route for improving the performance of solution‐processed Ga 2 O 3 solar‐blind photodetectors.