Recombination of Alloy‐Trapped Excitons in Ternary Solid Solutions with Common Cation Components

A new analysis of absorption and photoluminescence (PL) spectra of CdS 1− x Se x and ZnSe 1− x Te x 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 (ϵ/ϵ PL ), the parameter E PL being proportional to the Urbach parameter ϵ 0 in the absorption spectra. This analysis provides the most direct evaluation of the concentration N 0 of localized tail states. The values N 0 a 3 = (4.5 ± 0.7) × 10 −3 and (2.5± 0.5) × 10 −3 are obtained for CdS 1− x Se x and ZnSe 1− x Te x respectively, which lead to the estimations N 0 ≈1.5 × l0 19 and ≈ 8 × 10 18 cm −3 in these solid solutions, using the previously determined value a ≈ 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.