Resonant Rayleigh Scattering in Epitaxially Grown ZnSe_1−xS_x Layers

Abstract

In recent years the development of blue light emitting devices led to an increasing interest in ZnSe/ZnS layer systems epitaxially grown on a GaAs substrate. Most important to understand the optical processes in these materials are the excitonic states. Contrary to bulk crystals, they are affected by intrinsic biaxial strain which occurs due to lattice mismatch and different thermal expansion between layer and substrate and which reduces the crystal symmetry from T _d to D _2d (for literature see e.g. ref.[1]). As a consequence, the fourfold degenerate valence band and, hence, the excitonic states are strain-split into heavy (hh) and light (lh) hole states, each twofold degenerate. In this contribution we present a study of the exciton properties by Resonant Rayleigh Scattering (RRayS). Originally introduced by Hegarty et al. ², RRayS represents a linear coherent spectroscopic method that hitherto was rarely applied but can provide information beyond that obtained by other optical techniques³.