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

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.