The growth and the characteristics of cadmium telluride thin films prepared by chemical vapour deposition

Abstract

A study has been made of the electrical properties of CdTe thin films prepared by chemical vapour deposition (CVD) using the direct combination of cadmium and tellurium on foreign substrates as a function of the deposition parameters. The experimental results indicate that the conductive type and the carrier density are not dependent on the Cd/Te molar ratio in the gas reaction mixture or on the doping concentration; they are controlled mainly by substrate temperature. The films are p-type at substrate temperatures above 550 degrees C and n-type at substrate temperatures below 520 degrees C. The carrier density varies with the substrate temperature. These conclusions are significantly different from previous reports on CdTe films prepared by the same method. In addition, the effect of different substrate materials on the electrical properties is discussed. A comparison between two kinds of CdTe films prepared by close-spaced vapour transport and by chemical vapour deposition using the direct combination of Cd and Te has been made. A convenient method of CdTe films deposited by CVD has been provided.