ZnO/MgO Schottky ultraviolet photodetector with high on/off ratio

Abstract

Low-cost, high-performance zinc oxide (ZnO) Schottky ultraviolet (UV) photodetectors (PDs) have garnered significant interest. However, due to the existence of defect states in solution-processed ZnO, the reduced carrier mobility limits the device's performance and further application. In this study, Schottky UV PDs were successfully prepared based on the ZnO/MgO composite films. The ZnO/MgO composite film's surface has a “gully” appearance when compared to the original ZnO thin films. The accumulation of uniform-sized grains creates irregular strip bumps, which increases the film's surface area and, consequently, its overall quality. The composite film exhibits excellent UV light absorption from 330 to 360 nm, and the reduced internal resistance results in fewer defects facilitating carrier migration. These superior characteristics significantly improve the device's photoelectric performance. It is worth noting that the device on/off ratio increases by 39 times (from 2.77 to 111.46), the noise equivalent power (NEP) and the normalized detectivity (D∗) decrease and increase by one order of magnitude, respectively, as the applied voltage increases from 1 to 2 V. Furthermore, the responsivity is improved by 3 times (from 0.46 to 1.88 mA W⁻¹), and response time is reduced by 42 %. This work provides a new idea for developing high-performance ZnO Schottky UV photodetectors.