Mechanisms of the degradation of Schottky-barrier photodiodes based on ZnS single crystals

The effect of ultraviolet (UV) illumination on the electrical and spectral characteristics of Schottky-barrier photodiodes based on ZnS single crystals is studied. It is found that irradiation deteriorates their photosensitivity and changes the current–voltage and capacitance–voltage characteristics and the surface profile of the blocking electrode. It is shown that the main reason for a decrease in the photosensitivity of the diodes is the photoinduced drift of mobile donors in the electric field of the barrier. This drift depends on the crystallographic orientation of the surface being irradiated. Another photoinduced process observed in the diodes is photolysis of the ZnS crystal. This process mainly determines the change in the electrical characteristics of the diodes and in the surface profile of the electrode at an insignificant change in the photosensitivity.