Broadband Ultraviolet Self-Powered Photodetector Constructed on Exfoliated <i>β-</i>Ga₂O₃/CuI Core–Shell Microwire Heterojunction with Superior Reliability

Abstract

A heterojunction is an essential strategy for multispectral energy-conservation photodetection for its ability to separate photogenerated electron-hole pairs and tune the absorption edge by selecting semiconductors with appropriate bandgaps. A broadband ultraviolet (200-410 nm) self-powered photodetector is constructed on the exfoliated <i>β-</i>Ga₂O₃/CuI core-shell microwire heterostructure. Benefiting from the photovoltaic and photoconductive effects, our device performs an excellent ultraviolet (UV) discriminability with a UVC/visible rejection ratio (<i>R</i>₂₂₅/<i>R</i>₆₀₀) of 8.8 × 10³ and a UVA/visible rejection ratio (<i>R</i>₄₀₀/<i>R</i>₆₀₀) of 2.7 × 10², and a self-powered photodetection with a responsivity of 8.46 mA/W, a detectivity of 7.75 × 10¹¹ Jones, an on/off switching ratio of 4.0 × 10³, and a raise/decay speed of 97.8/28.9 ms under UVC light. Even without encapsulation, the photodetector keeps a superior stability over ten months. The intrinsically physical insights of the device behaviors are investigated via energy band diagrams, and the charge carrier transfer characteristics of the <i>β-</i>Ga₂O₃/CuI interface are predicted by first principle calculation.