EXCITONIC LUMINESCENCE AND THE EFFECT OF HIGH-EXCITATION IN ZNSE-ZNS STRAINED-LAYER SUPERLATTICES GROWN ON ZNS SUBSTRATES

Excitonic properties of the ZnSeZnS MQW strained-layer superlattices (SLSs), fabricated on (100) ZnS and GaAs substrates by a low-pressure metalorganic chemical vapour deposition method, have been investigated by means of photoluminescence and absorption spectra. With increasing excitation density by a N2 pulsed laser, it was found that a dominant exciton band moves toward higher photon energy. In order to understand the dissociation mechanisms of excitons, the temperature dependence of the linewidth and emission intensity obtained under high excitation was explicitly measured. The linewidth on temperature can be analyzed by considering three contributions which are related to scatterings of excitons with LO and acoustic phonons, and with donor impurities. The activation energy of about 71 meV for the thermal liberation of excitons can be obtained and is close to approximately 4EB,3D (the binding energy EB,3D=19 meV in ZnSe bulk). © 1989.