Abstract: Graphene monolayer has been extensively applied as a transparency electrode material in photoelectronic devices due to its high transmittance, high carrier mobility, and ultrafast carrier dynamics. In this study, a high-performance self-powered photodetector, which is made of a SnO₂ microwire, p-type GaN film, and monolayer graphene transparent electrode, was proposed and fabricated. The detector is sensitive to ultraviolet light signals and illustrates pronounced detection performances, including a peak responsivity ∼ 223.7 mA W^-1, a detectivity ∼ 6.9 × 10¹² Jones, fast response speed (rising/decaying times ∼ 18/580 µs), and excellent external quantum efficiency ∼ 77% at 360 nm light illumination without external power supply. Compared with the pristine SnO₂/GaN photodetector using ITO electrode, the device performances of responsivity and detectivity are significantly increased over 6 × 10³% and 3 × 10³%, respectively. The performance-enhanced characteristics are mainly attributed to the high-quality heterointerface of n-SnO₂/p-GaN, the highly conductive capacity, and the unique transparency of graphene electrodes. Particularly, the built-in potential formed at the SnO₂/GaN heterojunction interface could be strengthened by the Schottky potential barrier derived from the graphene electrode and SnO₂ wire, enhancing the carrier collection efficiency through graphene as a charge collection medium. This work is of great importance and significance to developing excellent-performance ultraviolet photodetectors for photovoltaic and optoelectronic applications in a self-powered operation manner.

Key words: Self-powered photodetector, SnO₂ microwires, Monolayer graphene electrode, Heterojunction, Schottky barrier