BOUND-EXCITONS AND BI-EXCITONS IN ZNCDSE ZNSE MULTIPLE-QUANTUM WELLS/

Using a set of high-quality MBE grown samples, a systematic study of b i- and bound-excitons in wide-gap II-VI quantum wells is carried out f or the first time. The assignment of low-energy photoluminescence line s to these complexes is accomplished by their characteristic polarizat ion properties in a magnetic field. The binding energy of the bi-excit on increases with growing band offset. A similar tendency is found for the bound-exciton, however, with generally smaller binding energies. The larger values found for the bi-exciton are attributed to localizat ion on alloy fluctuations which is qualitatively confirmed by density functional calculations. Time-resolved photoluminescence is used to st udy the formation and decay kinetics of bi-excitons.