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

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journal contribution
posted on 24.09.2020, 13:05 by Chandan Samanta, Sekhar Bhattacharya, A. K. Raychaudhuri, Barnali Ghosh
We report a high-response optical detector based on n-ZnO/p-Si nanowires (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 broadband 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 photodetector uses n-ZnO as the active photoconductive channel that is sensitive in the UV region. However, using photogating as well as favorable 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 broadband performance. We observed significant enhancement of responsivity R not only in the visible range but also in the UV and NIR region with a high detectivity of 1011 cm Hz1/2 W–1. The responsivity of the detector is ∼1 A/W from 700 nm to a longer wavelength (at a bias of 1 V) and, in the visible region, the responsivity of the photodetector with Au NPs is >0.5 A/W and increases to >1 A/W in the UV region.