RECOMBINATION DYNAMICS OF LOCALIZED EXCITONS IN A CDSE ZNSE/ZNSXSE1-XSINGLE-QUANTUM-WELL STRUCTURE/

Optical properties of localized excitons have, been studied in a highl y strained CdSe quantum well with 1-ML thickness by employing time-res olved photoluminescence (PL) and nonlinear PL spectroscopy under vario us excitation conditions. At 20 K, the time-integrated PL from the wel l layer was peaked at 2.7276 eV with a linewidth of 21 meV under low e xcitation intensity (0.11 mu J/cm(2)). The lifetime ranged from 200 ps to 50 ps as the monitored photon energy was changed from the low-ener gy tail to the high-energy one. The behavior could be well understood as a result of exciton localization, which is induced by terraces and islands with units of ML thickness fluctuation lying at the interface between CdSe and ZnSe. An emission with the fast decay component was o bserved at the low-energy side of the peak (2.7168 eV) under higher ex citation condition. The emission could be well resolved as a positive component by the,nonlinear PL measurement, and originates from the man y-body effect of localized excitons, which is probably attributed to l ocalized biexcitons.