Localisation of excitons at small Te clusters in diluted ZnSe1-xTexsolid solutions

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Abstract
The low-temperature recombination luminescence of ZnSe1-xTex solid solutions is studied in the Te concentration range 1%<or=x<or=2%. The dependence of the spectra on Te content and on excitation photon energy allows the authors to discriminate three different emission components. They are ascribed to recombination of excitons localised at clusters very probably consisting of two and more than two Te atoms. Selective excitation reveals substantial inhomogeneous broadening of states due to fluctuations in the local environment of the clusters. The phonon side-band structure concomitantly observed gives strong support to their model in which the large-radius exciton is tightly bound through the hole. The excitation spectra of the LO phonon replica intensity and of its polarisation degree provide information on the energy distribution of the localised states and their dynamic properties. The strong modification of the localised state emission spectrum found at higher Te concentration can be qualitatively understood by the increasing cluster interaction.