MICROPROBE SPECTROSCOPY OF LOCALIZED EXCITON STATES IN II-VI QUANTUM WELLS

We have investigated exciton localization in Zn1−xCdxSe/ZnSe quantum wells by microprobe, spatially resolved luminescence. We found that compositional fluctuations in Cd-rich (x=0.23) quantum wells induce the formation of a tail of states in the gap, where a continuum of localized exciton states forms. On the other hand, shallow quantum wells (x=0.11) exhibit sharp lines due to excitons localized at monolayer well-width fluctuations extending over a few hundred nanometers. The observed results are consistent with the occurrence of localized exciton lasing in deep ZnCdSe quantum wells.