PHOTOLUMINESCENCE OF ZNS1-XSEX - TE PREPARED BY SOLUTION GROWTH USING SB-CHALCOGENIDES AS SOLVENT

Photoluminescences due to Te isoelectronic traps were investigated for Te-doped ZnS1-xSex crystals (0 less than or equal to x less than or equal to 1) grown from Sb-chalcogenide solutions. The optical depths of the isolated Te atom center and the nearest-neighbor Te-Te pair center were determined from the emission spectra and the excitation spectra at 77 K. These depths decreased monotonically with increasing Se composition x. The theoretical relation between the optical depth and the composition x on the basis of the Koster-Slater one-band one-site approximation was best fitted to the experimental data by assuming the values of the matrix element of the impurity potential J(ZnS:Te) = 2.41 eV, J(ZnSe:Te) = 1.27 eV, and the effective width of the valence band T-ZnS = 6.02 eV, T-ZnSe = 6.21 eV. According to the criteria in the theory, excitons bound to the isolated Te atoms exist in ZnS1-xSex:Te for 0 less than or equal to x < 0.85 and excitons bound to the Te-Te pairs exist throughout the entire composition range. The emission band observed at 2.61 eV in ZnSe:Te was shown to be due to the excitons bound to the Te-Te pairs.