Excitons as a probe of interface morphology in Cd(Zn) Se/ZnSe heterostructures

We present studies of the excitonic spectrum in superlattices (SLs) of CdSe insertions in a ZnSe matrix aimed at elucidating the CdSe/ZnSe interface m orphology. The experimental photoluminescence excitation spectra are compar ed with the results of variational exciton calculations performed within th e effective mass approximation. The shape of the average vertical (along th e SL growth axis) distribution of CdSe within each insertion, used in the c alculations, was obtained from a theoretical simulation of X-ray diffractio n (XRD) rocking curves measured in the same samples, The results indicate t hat the thinnest layers are graded composition ZnCdSe quantum wells (QWs), generally homogeneous in the layer planes, whereas flat islands enriched by Cd appear at the CdSe nominal thickness larger than 0.5-0.6 monolayer (ML) . (C) 2000 Elsevier Science B.V. All rights reserved.