High-performance phototransistor-based solar-blind (200-280 nm) ultraviolet (UV) photodetectors (PDs) are constructed with a low-cost thin-film ZnO/Ga2O3 heterojunction. The optimized PD shows high spectral selectivity (R254/R365 > 1 × 103) with a photo-to-dark current ratio of ∼104, a responsivity of 113 mA/W, a detectivity of 1.25 × 1012 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/Ga2O3 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/Ga2O3 heterojunction phototransistor is a promising candidate for highly sensitive solar-blind PDs.
Keywords: UV phototransistors; ZnO/Ga2O3 heterojunction; high spectral selectivity; solar-blind photodetector; thin-film transistors.