EXCITONIC PROPERTIES OF ZINCBLENDE ZNSE MGS SUPERLATTICES STUDIED BY REFLECTION SPECTROSCOPY/

Excitonic properties of newly developed zinc-blende ZnSe/MgS superlatt ices (SL's) were measured by reflection spectroscopy. The modification of the excitonic peaks by the multiple reflection in the SL films was treated theoretically and a fitting method to estimate the exciton ab sorption peak positions and exciton linewidths was developed. Although zinc-blende MgS did not exist before, excellent optical properties we re observed in the ZnSe/MgS SL's. Excitonic structures were clearly ob served from 13 K up to the measured room temperature. In spite of stro ng ionicity of MgS barrier layers in the ZnSe/MgS SL's, the reduction of exciton-LO-phonon coupling was clearly observed in narrower wells. This indicates that the quantum confinement effect on excitons is larg e due to the large band offsets and it overcomes the enhancement of ex citon-LO-phonon scattering due to high ionicity in barrier layers.