High-performance gate-all-around phototransistor with a Ga₂O₃/NiO heterojunction for advanced ultraviolet detection

Gallium oxide (Ga₂O₃), with its ultra-wide bandgap of 4.9 eV, excellent thermal stability, and availability in large native substrates, is an ideal material for solar-blind ultraviolet (UV) detection. In this study, we present a high-performance gate-all-around (GAA) phototransistor based on a p-NiO/n-Ga₂O₃ heterojunction, specifically designed for advanced UV detection applications. The incorporation of p-NiO as the gate material provides a strong built-in electric field, which significantly improves carrier separation, suppresses dark current, and enhances the overall photoresponse. The constructed GAA phototransistor exhibits superior optoelectronic properties, including a responsivity of 8.64×10⁶A/W, an external quantum efficiency of 4.23×10⁹%, a detectivity of 9.92×10¹⁹ Jones, and rise/fall times both of 5 µs. Comprehensive simulation and experimental analyses reveal that the enhanced performance stems from the favorable type-II band alignment at the NiO/Ga₂O₃ interface, which facilitates efficient photocarrier generation and transport. This work not only establishes a pathway for developing high-sensitivity and fast-response UV photodetectors but also lays the foundation for further advancements in solar-blind optoelectronics for environmental monitoring, space exploration, and other critical applications.