Reduction of the Cd0.9Zn0.1Te surface conductivity by chemical treatment

Abstract

The influence of Cd0.9Zn0.1Te crystals pretreatment on the effectiveness of the passivation was studied. The optimal conditions of passivation process are determined. Samples of Cd0.9Zn0.1Te were treated with Br2-DMF solution before the investigation. After treatment the surface of the sample was smooth without visible irregularities, which indicates the good polishing properties of this etching solution and the possibility of using the samples for further study. Passivation of samples surface was carried by the NH4F-H2O2 solution. The qualitative and quantitative composition of the Cd0.9Zn0.1Te sample surface was investigated by means of energy-dispersive X-ray spectroscopy (EDX). The formation of a uniform oxide surface layer was confirmed. The electrical characteristics of the passivated samples were investigated by measurent the current-voltage dependences. The expediency of applying of the Cd0.9Zn0.1Te sample treatment in 50% KOH solution after their chemical treatment in the NH4F-H2O2 solution was proved. It was shown that after etching, excess tellurium appears on the surface of the specimens and causes increasing surface conductivity. Measurement of current-voltage dependencies for pre-treated specimens with and without KOH solution showed that the application of this additional chemical treatment step leads to a significant increase in the surface resistance of the specimen. Visual changes in the surface are also observed. It was found that the optimal conditions for Cd0.9Zn0.1Te crystals surface passivation are chemical treatment with NH4F-H2O2 solution for 2 min at a temperature of 18 °C. The current-voltage characteristics of the sample Cd0.9Zn0.1Te were measured at different stages of surface treatment: after polishing, after etching and after passivation. It was done for compares the overall effect of the semiconductor's surface quality on their electrical properties.