High-Performance Solar-Blind UV Phototransistors Based on ZnO/GaO Heterojunction Channels.

High-performance phototransistor-based solar-blind (200-280 nm) ultraviolet (UV) photodetectors (PDs) are constructed with a low-cost thin-film ZnO/GaO heterojunction. The optimized PD shows high spectral selectivity (R254/R365 > 1 × 10) with a photo-to-dark current ratio of ∼10, a responsivity of 113 mA/W, a detectivity of 1.25 × 10 Jones, and a response speed of 41 ms under 254 nm UV light irradiation. It is found that the gate electrode of a three-terminal phototransistor can amplify the responsivity and increase the photo-to-dark current ratio because of the different densities of field-induced electrons at different gate biases. In addition, the built-in electric field at the ZnO/GaO heterojunction interface can control the distribution of the photoinduced electrons and the total conductivity of the heterojunction, which can further enhance device performance. Together with the simple fabrication process, the achieved results suggest that the three-terminal ZnO/GaO heterojunction phototransistor is a promising candidate for highly sensitive solar-blind PDs.