Improvement in the Photocurrent to Dark Current Contrast Ratio of ZnO/Au Schottky Photodetector with PMMA Microlens Arrays

Abstract

A method is proposed to improve the photocurrent to dark current contrast ratio for the ZnO nanowire/Au Schottky barrier diode fabricated using dielectrophoresis to align the nanowires. Because the leakage current would lead to a large background noise, a poly(methyl methacrylate) (PMMA) layer is first employed as the passivation layer to cap on the surface of the ZnO nanowire Schottky diode; furthermore, the microlens array (MLA) structures are added to improve the light trapping effect and to magnify the probability of the photons to be absorbed by ZnO nanowires. After depositing the PMMA capping layer, the leakage current can be reduced by more than , whereas the contrast ratio can be increased from to at −1.0 V after the MLA structures are added on the diode.