High-performance self-powered ultraviolet photodetector in SnO2 microwire/p-GaN heterojunction using graphene as charge collection medium

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.