Role of metallic-like conductivity in unusual temperature-dependent transport in n-ZnO:Al/p-Si heterojunction diode

The current-voltage characteristics of an n-ZnO:Al(AZO)/p-Si heterojunction diode is investigated over a temperature range of 293 and 423 K. The measured current-voltage characteristics show good rectification behaviour at all temperatures. It is observed that the AZO/Si heterojunction exhibits different (unusual) types of charge conduction processes in the temperature range under consideration. In addition, temperature-dependent resistivity measurements performed on a AZO thin film grown on a glass substrate show metallic-like conductivity, which is explained on the basis of local annealing of defects, mainly vacancies, in the AZO layer. Finally, based on our experimental findings, we construct a parametric phase diagram to elucidate the transition from one to the other conduction mechanism. The present study will be useful to understand the effect of self-heating for AZO-based devices.