Self-Powered Photoelectrochemical (Al,Ga)N Photodetector with an Ultrahigh Ultraviolet/Visible Reject Ratio and a Quasi-Invisible Functionality for 360° Omnidirectional Detection

Self-powered ultraviolet (UV) photodetectors (PDs) are promising and essential for the applications of next-generation optoelectronic devices. This work proposes and demonstrates a self-powered photoelectrochemical (PEC) PD with three excellent characteristics successfully, which are the ultrahigh transmissivity, ultrahigh UV/visible reject ratio and responsivity. Thanks to the ultrahigh transmissivity, the PD can achieve the critical factor of quasi-invisible functionality to realize the 360° omnidirectional detection. Due to the angle-dependent photoresponsivity, this PEC PD can be utilized for quickly identifying the light direction. Furthermore, as the epitaxial substrate can have a nonignorable visible response, the key reason for obtaining the ultrahigh UV/visible reject ratio and excellent detection selectivity should be the removal of the epitaxial substrate. It is also found that the SiO2 layer can significantly enhance the photoresponsivity by suppressing the leakage current. With a demonstrated high stability, this PD would enable a broad range of optoelectronic applications, including 360° omnidirectional detection and UV communication.