Ultrasensitive, Superhigh Signal-to-Noise Ratio, Self-Powered Solar-Blind Photodetector Based on n-Ga2O3/ p-CuSCN Core-Shell Microwire Heterojunction

Abstract

Solar-blind photodetectors have captured intense attention due to their high significance in ultraviolet astronomy and biological detection. However, most of the solar-blind photodetectors have not shown extraordinary advantages in weak light signal detection because the forewarning of low-dose deep-ultraviolet radiation is so important for the human immune system. In this study, a high-performance solar-blind photodetector is constructed based on the n-Ga₂O₃/p-CuSCN core-shell microwire heterojunction by a simple immersion method. In comparison with the single device of the Ga₂O₃ and CuSCN, the heterojunction photodetector demonstrates an enhanced photoelectric performance with an ultralow dark current of 1.03 pA, high photo-to-dark current ratio of 4.14 × 10⁴, and high rejection ratio (R₂₅₄/R₃₆₅) of 1.15 × 10⁴ under a bias of 5 V. Excitingly, the heterostructure photodetector shows high sensitivity to the weak signal (1.5 μW/cm²) of deep ultraviolet and high-resolution detection to the subtle change of signal intensity (1.0 μW/cm²). Under the illumination with 254 nm light at 5 V, the photodetector shows a large responsivity of 13.3 mA/W, superb detectivity of 9.43 × 10¹¹ Jones, and fast response speed with a rise time of 62 ms and decay time of 35 ms. Additionally, the photodetector can work without an external power supply and has specific solar-blind spectrum selectivity as well as excellent stability even through 1 month of storage. Such prominent photodetection, profited by the novel geometric construction and the built-in electric field originating from the p-n heterojunction, meets greatly well the "5S" requirements of the photodetector for practical application.

Keywords: Ga2O3/CuSCN; core−shell microwire; photodetector; p−n heterojunction; solar blind; ultrasensitive.