Spatially resolved near-field photoluminescence spectroscopy of II-VI quantum wells: The role of localized excitons

Excitons localized at compositional potential fluctuations are individually resolved by spatially resolved near-field luminescence in ZnCdSe/ZnSe quantum wells at room temperature. Localization is found to occur on a scale length of about 100 nm, in Cd-rich clusters in which the local Cd content varies by approximately 1% with respect to the nominal composition, and in steps of about 0.3%. A microscopic modeling of the localized exciton states is presented, which describes quite well the observed near-field spectra.