Ultrahigh-responsivity deep-UV photodetector based on heterogeneously integrated AZO/a-Ga2O3 vertical structure

Abstract

ZnO:Al (AZO) and a-Ga2O3 thin films were successively deposited on a sapphire substrate by magnetron sputtering and the photoelectric properties of AZO/a-Ga2O3 heterojunction vertical structure to solar blind ultraviolet light were investigated. The device shows a high photo-to-dark current ratio (2.2 × 103), low dark current (11.4 nA), large responsivity (67.26 A/W) and fast response and recovery times of 1.53 μs and 2.25 ms under 254 nm light illumination at 10 V. Additionally, the device exhibits an obvious self-powered effect with light-dark current ratio (183.3) and the responsivity (2.92 × 10−2 A/W) at 0 V. The high response is attributed to the separation of photogenerated electron-hole pairs due to built-in field in the depletion width of AZO and Ga2O3. The analysis shows that there exists a quasi-Zener tunneling internal gain mechanism, which increases the performance of the device. The comprehensive performance of the device implied a wide potential in optoelectronics applications.