Enhancing Hot-Electron Photodetection of a TiO2/Au Schottky Junction by Employing a Hybrid Plasmonic Nanostructure.

Abstract

Hot-electron photodetectors (HEPDs) are triggering a strong surge of interest in applications of image sensors and optics communication, since they can realize photoelectric responses when the incident photon energy is lower than the bandwidth of the semiconductor. In traditional HEPD systems, the metal layers are dressed with regular gratings, which can only excite plasmonic resonance over a narrow bandwidth, limiting the hot-electron photoelectric effect. To break this limitation, hybrid plasmonic nanostructures should be applied in HEPDs. Here, we propose a TiO2 based HEPD device incorporated with a hybrid plasmonic nanostructure, which consists of Au nanoparticles (Au NPs) and a conformal transparent Au film. With the assistance of the plasmonic resonances excited in this hybrid nanostructure, the spectrum of the photocurrent response is significantly broadened from the UV band to the visible and near-infrared (NIR) ranges. It is demonstrated that at the wavelengths of 660 nm and 850 nm, the photocurrent in the hybrid HEPD device is enhanced by 610% and 960%, respectively, compared with the counterparts without the addition of Au NPs. This work promotes the development of high performances HEPDs, offering an alternative strategy for realizing photodetection and image sensing in the NIR range.