Effect of the pos-deposition annealing with CdCl2 on the optical, structural and morphological properties of CdTe-films grown by CSS

A set of CdTe films grown by the CSS method were annealed in aCdCl(2) atmosphere of during 5 min at 345, 365, 385, 405, 425, 435, 445 and 455 degrees C. The films were characterized before and after annealing by the SEM, EDS, X-ray, optical absorption and photoluminescence (PL) techniques. As the annealing temperature is increased a tendency to improve the Cd/Te ratio is observed. After the thermal treatment at 430 degrees C the films reach the stoichiometry. A deviation from stoichiometry appears again for annealing temperatures higher than 430 degrees C. The PL spectra of the films at 6.5 K exhibit two emission bands, one corresponds to the defects energy levels band (1.4-1.5 eV) and the other is located in the interval from 1.564 to 1.584 eV (pA). For annealing temperatures higher than 430 degrees C an increment in the intensity and energy position of pA is observed, while for annealing temperatures less than 430 degrees C the behavior is irregular. In the emission mechanisms of pA the expected impurities and/or native defects in the material such as the V-Te, VCdClTe, Cd-Te and Cl-Te are involved.