Electrical study of ZnO film thickness effect on the evolution of interface potential barrier of ZnO/p-Si heterojunction: Contribution to transport phenomena study

In this work, we have studied the evolution of the potential barrier of ZnO/Si hetero-junction interface and we have experimentally highlighted an interface state defect that controls the conduction of the charge carriers. The samples were elaborated by DC reactive sputtering method, under controlled ambient mixture gas of Ar/O2. The study consists of the effect of the ZnO film thickness on the evolution of the potential barrier at the interface profile. The determination of the defects controlling the conduction is investigated by thermally stimulated current technique. The results showed that the electrical conduction is controlled by defects situated close to the conduction band of ZnO with activation energy of 0.35 eV. However, their density influences considerably both the rectification of n-ZnO/p-Si hetero-junction diode and the transport phenomena through the interface. Effectively, the current-potential-temperature measurements showed that when the thickness varied from 30 to 100 nm, the conduction mechanism at the n-ZnO/p-Si interface changed from tunneling through the potential barrier model to the diffusion over the potential barrier.