Polycrystalline Ga₂O₃ Nanostructure-Based Thin Films for Fast-Response Solar-Blind Photodetectors

Polycrystalline Ga2O3 nanostructure-based thin films were prepared by electron beam evaporation, followed by annealing treatment. The microstructure and optical properties of the unannealed and 800 °C annealed Ga2O3 thin films were characterized. The results showed that the 800 °C annealed Ga2O3 thin films have larger grains and shorter UV absorption wavelength in comparison with the unannealed Ga2O3 thin films. A metal/semiconductor/metal-structured photodetector based on Ga2O3 thin films was fabricated, and the UV photoresponse performances were investigated. The photodetector using an annealed Ga2O3 thin film exhibited low dark current (163 pA @ 0.25 V/μm) and high responsivity rejection ratio (R254 nm/R310 nm = 3.2 × 103). Significantly, under 266 nm laser pulse illumination, the annealed Ga2O3 thin-film photodetector shows fast response rise time (16.6 μs) and fall time (196.7 μs), respectively, which are faster than that of most of the reported gallium oxide solar-blind photodetectors. The fast response was attributed to the reduced defect and grain boundaries in the annealed Ga2O3 thin film. This work provides guidelines to the preparation of large-area, low-cost, and high-crystalline Ga2O3 nanostructure-based thin films and is promising to realize high-sensitivity and real-time response solar-blind photodetectors.