High response MSM UV photodetectors based on MgZnO/MnS heterojunction

Abstract

Ultraviolet (UV) photodetectors (PDs) are favored for their wide range of applications. In this work, MgZnO/MnS composite films were prepared on quartz glass by sol-gel and successive ionic layer adsorption and reaction (SILAR) methods for UV photodetection. Compared with MgZnO device, the MgZnO/MnS device overcomes the drawbacks of lower carrier mobility and more traps in the original MgZnO photosensitive layer, and has ultrahigh responsivity and detectivity (4564.5 A/W, 1.7 × 1016 Jones), high photocurrent (up to 1.8 × 10−3 A), lower dark current (down to 8.8 × 10- 10 A) and high light-dark ratio (up to about 8 × 105), which is attributed to the formation of a p-n junction by the contact between MgZnO and MnS, resulting in the establishment of an internal electric field to serve as a depletion layer. The built-in electric field consumes most of the carriers so that the device exhibits a low conductivity, and MnS fills up some of the defects on the surface of the MgZnO, which results in a low dark current. Under UV radiation, photogenerated carriers are separated by built-in electric field, leading the recombination of electron-hole pairs decrease. This causes the device show high conductivity and generate high photocurrent. These results make MgZnO/MnS PDs promising for applications in device requiring high responsivity.