Characterization of Foreign Atoms and Native Defects in Single Crystals of Cadmium Telluride by High-Temperature Conductivity Measurements

A method of determining the purity of CdTe which may also be applicable to other compound semi-conductors is presented. The electrical conductivity of undoped and lightly doped CdTe was studied from 600 to 900°C as a function of the partial pressures of its components. At high tellurium over-pressures the conductivity is independent of partial pressure. The conductivity of undoped material depends exponentially upon temperature with an activation energy characteristic of intrinsic conduction. For indium-doped CdTe and for material containing impurities the intrinsic conductivity levels off with a reduction in temperature and becomes characteristic of the foreign atom concentration.