Photoconductivity and photoluminescence in chemically deposited films of CdSSe:CdCl2,Ho

Results of the scanning electron microscopy (SEM), X-ray diffraction (XRD), optical absorption, photoconductivity (PC), and photoluminescence (PL) studies for the CdSSe:CdCl₂,Ho films are presented in this paper. The SEM studies of different CdSSe films show a layered growth structure. A crystalline nature of the films is observed in the XRD studies. The regions with stacking fault were also observed in the X-ray diffractograms. The optical absorption spectra of these films show variations corresponding to the band gaps and the grain-sizes obtained under various deposition conditions and also with annealing. The effect of flux, impurities and annealing on the saturated photo to dark current ratio I_pc/I_dc is observed in the PC rise and decay studies. The maximum value of I_pc/I_dc ∼10⁷ is obtained for the impurity doped annealed films. The PL emission spectra of CdSSe films show two emission peaks associated with the annihilation of free excitons and the transitions between shallow donor and deep acceptor states. In CdSSe:CdCl₂,Ho films, two PL emission peaks are observed at 495 nm and 545 nm corresponding to the transitions ⁵S₂→⁵I₈ and ⁵F₃→⁵I₈, respectively, in Ho. The effect of pH on PL and grain size is also included in the present studies.