Abstract
We investigated the role of excitons, biexcitons and free-carriers in Zn1–xCdxSe/ZnSe multiple quantum well structures. By using stimulated emission measurements, pump and probe absorption spectroscopy, and magnetoluminescence we determined the threshold for exciton bleaching and lasing. The threshold for lasing resulted to be less than 10~kW~ cm–2regardless of sample structure and composition, whereas the threshold for exciton bleaching was found to be larger or smaller than this value, depending on the exciton binding energy and localization effects. The competition between excitons, biexcitons and free-carriers in the stimulated emission processes is thus discussed in terms of a phase diagram model.
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