Au-Mediated Surface Plasmon Enhanced Ultraviolet Response of p-Si/n-ZnO Nanorods Photodetectors

Surface plasmon resonance mediated by Gold (Au) nanoparticles (NPs) was employed to enhance the ultraviolet (UV) response of p-Si/n-ZnO nanorod (NR) heterojunction photodetectors (HPDs). In the ZnO NRs with Au NP covering, the photoluminescence spectrum shows that the band-to-band emission of ZnO (384 nm) is increased by a magnitude of 3, and the deep-level emissions (450-700 nm) are drastically decreased as compared with HPDs without coverings of Au NPs. Such a result increases UV-to-visible rejection ratio from 214 to 6180 and it attributes that the defect-level emissions of ZnO induce surface plasmon resonance in Au NPs and then enhances the emissions, exciting a large quantity of electrons crossing over the Au NP/ZnO interface barrier. Consequently, these electrons are transferred to the ZnO conduction band from the Au NPs, causing a photocurrent gain and the quantum efficiency is as high as 1157% at 2 V reverse bias.