Broadband (Ultraviolet to Near-Infrared) Photodetector Fabricated in n-ZnO/p-Si Nanowires Core–Shell Arrays with Ligand-Free Plasmonic Au Nanoparticles

Abstract

We report a high response optical detector based on n-ZnO/p-Si NWs core-shell arrays decorated with plasmonic Au nanoparticles (NPs), that works in the broad frequency range from UV (300 nm) to NIR (1100 nm) and consumes low power (few μW). The optical detector combines the visible and NIR detectability of Si NWs with the UV detectivity of ZnO through the core- shell structure and broad band detectivity in the visible range has been achieved by decorating core -shell arrays with ligand-free Au NPs synthesized by using pulsed laser ablation in liquid. The photo-detector uses n-ZnO as the active photoconductive channel that is sensitive in UV region. However, using photo-gating as well as favourable band alignments the carriers generated at longer wavelengths in visible and NIR in Au NPs and Si NWs arrays were introduced into the conduction band of ZnO leading to its broad band performance. We observed significant enhancement of responsivity R not only in visible range but also in UV and NIR region with a high detectivity of 1011 (cmHz1/2W-1). The responsivity of the detector ~ 1 A/W from 700nm to longer wavelength (at bias of 1V) and in the visible region the responsivity of the photo detector with Au NPs is > 0.5 A/W and increases to > 1 A/W at UV region.