Self-powered solar-blind ultraviolet-visible Cu2O/Ga2O3 photodetectors

Abstract

Traditional optical communication using single narrow-band photodetectors (PDs) has poor confidentiality because all information and data are exposed to free space. With the development of science and technology, even the optical communication in the solar-blind ultraviolet (UV) band carries the risk of eavesdropping. Dual-band PDs have potential applications in secure and reliable optical communication through a combination of optical encryption and algorithmic encryption. In this paper, self-powered Cu₂O/Ga₂O₃ heterojunction PDs with solar-blind UV-visible photodetection were fabricated. By adjusting the pH value of the Cu₂O electrolyte, the crystallization quality and grain orientation of the Cu₂O thin film were improved, and the interface transfer resistance of the heterojunctions was decreased. The Cu₂O/Ga₂O₃ PDs fabricated in Cu₂O electrolyte with a pH value of 9.5 demonstrated the optimized solar-blind UV-visible photoresponse characteristics. In the absence of applied bias, the device exhibited a responsivity of 0.12 mA W⁻¹, a rise time of 2.48 ms and a fall time of 11.72 ms at 254 nm. The responsivity reaches 19 mA W⁻¹ when illuminated at 475 nm, and the rise and fall times are 0.96 and 9.12 ms, respectively. Utilizing the excellent photoresponse characteristics of the solar-blind UV-visible band, the device was used to design and demonstrate a proof-of-concept optical communication system for secure data transmission. The proposed system features two independent light channels, utilizing solar-blind UV light as the information carrier and visible light for key transmission. By implementing specific algorithms, this design ensures safe and reliable communication.