The effect of postannealing on the electrical properties of well-aligned n-ZnO nanorods/p-Si heterojunction

This work investigates the effects of postannealing on the electrical properties of the n-ZnO nanorods/p-Si heterojunction. Well-aligned ZnO nanorods are grown on the p-Si substrate with a ZnO seed layer through a hydrothermal method. The as-grown ZnO nanorods are grown along the preferential [0001] direction with high single crystalline quality. The rectifying characteristics of the heterojunction are effectively improved and the rectification ratio is increased tens of times after annealing in air. The leakage current is decreased by two orders of magnitude and the forward-bias injection efficiency is largely enhanced after annealing. The photoluminescence and x-ray photoelectron spectroscopy results show that annealing in the air ambient can effectively reduce the loosely adsorbed oxygen on the surface of the ZnO nanorods so that the bound free electrons can be released, which can result in larger carrier concentration and improve the injection efficiency of the n-ZnO nanorods/p-Si structure in the forward voltage.