Hot-electron Injection in Au Nanorod-ZnO Nanowire Hybrid Device for Near-infrared Photodetection

In this Letter, we present a new class of near-infrared photodetectors comprising Au nanorods-ZnO nanowire hybrid systems. Fabricated hybrid FET devices showed a large photoresponse under radiation wavelengths between 650 and 850 nm, accompanied by an "ultrafast" transient with a time scale of 250 ms, more than 1 order of magnitude faster than the ZnO response under radiation above band gap. The generated photocurrent is ascribed to plasmonic-mediated generation of hot electrons at the metal-semiconductor Schottky barrier. In the presented architecture, Au-nanorod-localized surface plasmons were used as active elements for generating and injecting hot electrons into the wide band gap ZnO nanowire, functioning as a passive component for charge collection. A detailed investigation of the hot electron generation and injection processes is discussed to explain the improved and extended performance of the hybrid device. The quantum efficiency measured at 650 nm was calculated to be approximately 3%, more than 30 times larger than values reported for equivalent metal/semiconductor planar photodetectors. The presented work is extremely promising for further development of novel miniaturized, tunable photodetectors and for highly efficient plasmonic energy conversion devices.