Stoichiometry of CdS crystals and their optical and lasing properties

The results of a complex optical investigation in vapor-phase-grown CdS single crystals with controllable stoichiometry are presented. The investigation was carried out by the spectroscopic methods of photoinduced absorption and of photoluminescence. The ratio of the partial pressures of cadmium and sulfur vapor components F = p(Cd)p(S2) at the crystallization front was used to change the properties of the crystals. A decrease of the concentration of the main identified deep centers was observed for crystals grown at log F ≈ 0.3. The maximum of the optical gain coefficient and the minimum of the plasma bimolecular recombination rate were previously obtained at the same value of F parameter. The CdS crystals grown under such conditions are expected to be of high quality and the latter is confirmed by the working parameters of scanning-electron-beam excited laser devices fabricated from the same CdS crystals.