Abstract
The effect of exciton localization is investigated in ZnCdS ternary alloys. Zn 1-x Cd x S films with Cd composition x(x=0.21-0.79) were prepared and transient optical properties of photoexcited excitons during the energy relaxation as well as steady-state photoluminescence (PL) properties are examined as a function of crystalline quality of the grown films. The sample with x=0.56 that is closely lattice matched to the GaAs substrate was found to show the maximum integrated band-edge PL (BEPL) intensity. The samples with larger lattice mismatch showed stronger quenching of the BEPL intensity, which is well correlated to the crystalline quality evaluated by X-ray rocking curve measurement. In order to study the contribution of exciton localization, time-resolved PL measurements were carried out. It is clearly revealed that the excitons fully relaxed to the localized states exhibit high luminescence efficiency, while the relaxation process of excitons toward the localization states is shown to be influenced by the crystalline quality of the films.
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