Performance of different Ga-doped ZnO nanosheets ultraviolet photodetectors: experimental and theoretical studies

High-performance and low-cost ultraviolet (UV) photodetector has always been the desired goals. In this work, Ga-doped ZnO (ZnO:Ga) nanosheets with different Ga doping concentrations from 0 to 6 mol% were synthesized by a hydrothermal method. Furthermore, six ZnO:Ga nanosheets UV photodetectors were fabricated by using the resulting ZnO:Ga nanosheets as the photosensitive layers, their UV detection performances were investigated in detail. The experimental results showed that the 1% Ga-doped ZnO nanosheets UV photodetector had the best performance among these devices, its responsivity was up to 100.2 A/W and response time was only 1.8 s. In addition, first-principles calculation was used to analyze the band structure and density of states from ZnO:Ga nanosheets with different doping concentrations. It was found that the 1% Ga-doped ZnO nanosheets had the narrowest band gap and the most concentrated conduction band density of states. The results indicated that proper Ga doping concentration could effectively improve photoelectric properties of ZnO:Ga nanosheets.