Highly Sensitive and Stable Self-Powered UV Photodetector Based on Amorphous ZnGa2O4/NiO Type-II p-n Heterojunction via Low-Temperature and Band Alignment

An effective p-n heterojunction fabrication strategy of amorphous ZnGa2O4/NiO self-powered ultraviolet (UV) photodetector is reported to consider both the low-temperature and band alignment. Owing to the excellent photovoltaic effect, the device exhibits an ultralow dark current of 1.81 pA, a satisfactory response sensitivity of 48.19 mA W-1, a specific detectivity of 1.9 x 10(12) Jones, and a high rise/decay speed of 41/22 ms under 255 nm light irradiation at 0 V bias. Compared with previously reported UV photodetectors, the proposed photodetector exhibits a high responsivity of 1.88 A W-1 and an excellent detectivity of 7.1 x 10(13) Jones under an applied voltage of -5 V, indicating its ability to detect weak signals. This remarkable photoelectric detection capability is attributed to the strong absorption of UV light by the amorphous ZnGa2O4 and typical type-II band alignment at the heterojunctions. Moreover, the photodetector continues to function stably without degradation, even after two months without an external power supply. This work not only provides an effective reference for the manufacture of high performance ZnGa2O4-based UV photodetectors, but also offers the opportunity for practical industrial production and flexible applications.