Electrical and optical properties of ZnO/Si heterojunctions as a function of the Mg dopant content

Abstract

Undoped and Mg-doped ZnO thin films prepared by a sol-gel process were deposited on p-Si and glass substrates via spin coating. The electrical and optical properties of the films were investigated. Atomic force microscopy images revealed that the ZnO films are formed from fibers consisting of nanoparticles. The electrical conductivity mechanism of the films was investigated. The I-V characteristics of Al/ZnO/p-Si samples showed rectification behavior with a rectification ratio that depended on the applied voltage and the Mg doping ratio. ZnO/p-Si heterojunction diodes exhibited non-ideal behavior with an ideality factor greater than unity that could be ascribed to the interfacial layer, interface states, and series resistance. The barrier height for undoped and Mg-doped ZnO/p-Si diodes was in the range 0.78-0.84 eV. The results demonstrate that the electrical properties of ZnO/p-Si heterojunction diodes are controlled by the Mg dopant content and suggest that the optical bandgap of these ZnO films can be tuned using the Mg level. © 2013 Elsevier Ltd. All rights reserved.