CHARACTERISTICS OF DEEP LEVELS IN N-TYPE CDTE

Deep-level transient spectroscopy has been employed to study the defect states in n-type CdTe crystals subjected to a variety of annealing treatments. By comparing the results from crystals grown by the Bridgman and travelling heater methods (starting from a common source of CdTe) and by considering the variation in properties with position along each boule, it was concluded that the electrical properties were strongly influenced by residual impurities in these materials. Eleven different defect states were detected with activation energies ranging from 0.2 eV to 0.86 eV. One of these was found only in In-doped samples and at least three were related to residual impurities and could be removed by annealing in liquid cadmium. Several defects were interpreted as complex centres involving native defects and impurities.