EXCITON COMPLEXES IN ZNSE LAYERS - A TOOL FOR PROBING THE STRAIN DISTRIBUTION

Differently acting strain components caused by lattice mismatch or deviating thermal expansion coefficients of ZnSe and any substrate material yield a typical thickness-dependent strain profile in ZnSe epitaxial layers. For the analysis of strain in those layers, the investigation of free and bound excitons is very suitable. In the present work, samples are used exhibiting surface strain magnitudes epsilon between -5 x 10(-4) (compressive in-plane strain) and + 15 x 10(-4) (tensile in-plane strain), determined from reflection loops of the strain-split free excitons X(lh) and X(hh). Whereas reflection spectroscopy scans the strain situation at the layer surface only, excitation and resonant Raman spectroscopy, in particular of donor-bound excitons (D0, X), give information about the strain distribution in the whole film. Based on the observed set of different (D0, X) transitions I2i, originating from excited single-hole states, we are able to predict the strain profile and the distribution of the main donors in the film.