RECOMBINATION OF ALLOY-TRAPPED EXCITONS IN TERNARY SOLID-SOLUTIONS WITH COMMON CATION COMPONENTS

A new analysis of absorption and photoluminescence (PL) spectra of CdS1-xSex and ZnSe21-xTex solid solutions at liquid helium temperature is presented. It is shown that the high-energy side of the luminescence band of excitons trapped in the band tail can be fitted by a simple exponential function exp(epsilon/epsilon(PL), the parameter epsilon(PL) being proportional to the Urbach parameter epsilon0 in the absorption spectra. This analysis provides the most direct evaluation of the concentration N0 of localized tail states. The values N0a3 = (4.5 +/- 0.7) x 10(-3) and (2.5 +/- 0.5) x 10(-3) are obtained for CdS1-xSex and ZnSe1-xTex, respectively, which lead to the estimations N0 almost-equal-to 1.5 x 10(19) and almost-equal-to 8 x 10(18) cm-3 in these solid solutions, using the previously determined value a almost-equal-to 0.7 nm. A new model for the energy relaxation of excitons through the localized tail states is suggested which takes into account exciton-phonon interactions and non-radiative recombination of excitons.