Researches of I–V-characteristics and CV-characteristics of structures fabricated on unannealed and annealed at high temperature (t= 900 C) p-Cd 1− x Zn x Te substrates have been carried out. The influence of the intrinsic point defects system of the base material p-Cd 1− x Zn x Te on the interface properties of ZnO: Al/n-CdS/p-Cd 1− x Zn x Te heterojunctions have been studied. The above structures have been fabricated by sequential deposition of CdS and ZnO: Al thin films on crystalline p-Cd 1− x Zn x Te by high-frequency magnetron sputtering. Based on the analysis of the I–V-characteristics in the region of forward and reverse biases, the relationship between the physical processes during heat treatment and the structural perfection of the transition area of the studied heterojunctions have been established.