High-Performance Solar-Blind UV Phototransistors Based on ZnO/Ga₂O₃ Heterojunction Channels

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.