Electro-optical studies in chemically deposited Sm/Pr doped (Cd-Pb) S films

Abstract

Results of photoconductivity, optical absorption, XRD & SEM studies have been presented for different (Cd- Pb)S films. From the photo-current curves <i>I</i>_PC<i>/I</i>_DC<i> </i>ratio of the order of 10⁵ is observed for undoped (Cd_0.95-P_0.05)S film which improves to 10⁶ for the systems prepared with NaF and Samarium/Praseodymium nitrate. Due to annealing of the films at 400^oC, dark current decreases to almost zero value along with a decrease in photo-current also but the ratio goes to very high value. From the analysis of decay curves, lifetime of the carriers, mobility and trap-depths are determined. The values of lifetime and mobility are found to increase in presence of impurities. Band-gaps determined from optical absorption and photoconductivity excitation spectral studies show a similar nature in presence of impurities· The direct band-gap is found for mixed films. XRD studies show crystalline nature and according to SEM studies layered growth of films takes place.