Defects in Chlorine-Doped CdTe Thin Films

摘要

The photoluminescence (PL) spectra and optoelectronic parameters of chlorine, copper and oxygen doped CdTe thin films are investigated. It is found that the as-grown samples have high resistivity and intense 1.4 eV PL band. Vacuum annealing decreases the intensity of the 1.4 eV PL band and resistivity of films what is attributed to outdiffusion of chlorine. Following annealing under tellurium vapor pressure that lowers the concentration of chlorine, fills tellurium vacancies and generates cadmium vacancies, increases the concentration of A-centers, further decreases the 1.4 eV PL band, quenches 1.2 eV PL band, forms 1.0 eV PL band and significantly decreases the p-type resistivity of film. Annealing under cadmium vapor pressure quenches the 1.0 eV PL band, increases 1.4 eV PL band and increases the resistivity of film. Copper codopant increases the intensity of the 1.4 eV PL band and resistivity of film. Copper together with oxygen dramatically increases the resistivity of film and the intensity of the 1.4 eV PL band, and causes photoconductivity. The formed defects and their influence to the changes in the film characteristics are discussed.