EXCITON SCATTERING PROCESSES IN ZNSE ZNSXSE1-X MQW STRUCTURES/

Inelastic excitonic scattering processes have been investigated in ZnS e/ZnSxSe1-x multiple-quantum-well structures of different well width a nd strain content. The free-exciton energies have been determined by p hotoluminescence excitation spectroscopy and compared with those calcu lated accounting for the actual strain contribution. All the samples s how strong luminescence related to bound or localized excitons. In str ain relaxed samples, the interaction of these states with free-electro ns gives rise to optical gain at low temperature. In addition, a stron ger stimulated emission is observable up to room temperature. The temp erature and pumping intensity dependences of this latter amplification process suggest that two different lasing mechanisms may be invoked, namely free-exciton-bound-exciton or free-exciton-longitudinal-optical -phonon inelastic scattering.