EXCITON SCATTERING PROCESSES IN ZNSE/ZNSXSE1-X MQW STRUCTURES

Inelastic excitonic scattering processes have been investigated in ZnSe/ZnSxSe1-x multiple-quantum-well structures of different well width and strain content. The free-exciton energies have been determined by photoluminescence excitation spectroscopy and compared with those calculated accounting for the actual strain contribution. All the samples show strong luminescence related to bound or localized excitons. In strain relaxed samples, the interaction of these states with free-electrons gives rise to optical gain at low temperature. In addition, a stronger stimulated emission is observable up to room temperature. The temperature 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.