STIMULATED AND SPONTANEOUS EMISSION STUDIES IN ZNS1-XTEX ZNSE STRAIN LAYER SUPERLATTICES/

The optical and light emitting properties of ZnSTe/ZnSe strained super lattices are investigated. The hhl-el exciton absorption peak is obser ved both in absorption and photoluminescence excitation spectra at low temperatures. The Stokes shift between the photoluminescence and abso rption peak is similar to 6 meV indicating that the recombining excito ns are only weakly localized and that the sample quality is high. Stro ng exciton-phonon coupling in the ZnSe wells is evidenced from the obs ervation of oscillatory peaks with energy separation of 31 meV in the PLE spectra. These result from hot excitonic creation and subsequent r elaxation via multiple longitudinal-optical phonon emission. Room-temp erature stimulated emission by photopumping in the deep-blue spectral region is also observed. An upper limit of the threshold carrier densi ty required to achieve lasing is estimated to be similar to 5 X 10(18) /cm(3) for the ZnSTe/ZnSe superlattices.