Junction Properties and Gap States of ZnO Thin Film Prepared by Sol-Gel Process

N-type ZnO thin films with a crack- and columnar-free structure were successfully prepared on p-type Si substrates by the sol-gel process. The current-voltage ( I - V ) characteristics of the heterojunction of n-ZnO/p-Si show a rectification, and the capacitance-voltage ( C - V ) characteristics show an approximately linear C -2 - V relationship in the reverse bias condition. In the ZnO thin film, two gap states located at 0.054 eV and 0.12 eV below the conduction band were measured by isothermal capacitance transient spectroscopy (ICTS).