OPTICAL, STRUCTURAL AND LATTICE DYNAMICAL PROPERTIES OF EPITAXIAL ZN1-YMGYSXSE1-X LAYERS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

The optical, structural and lattice dynamical properties of Zn1-yMgySx Se1-x epilayers grown by low pressure metalorganic vapour phase epitax y were investigated. The composition of these layers, determined by el ectron probe microanalysis, was varied in the range of 0 less than or equal to x, y less than or equal to 0.2. Photoluminescence measurement s in the temperature range between 14 and 300 K were performed. The al loy broadening of the bandedge emission depending on the composition o f the layer was calculated on the basis of a binomial statistical mode l. The comparison between the measured bandedge photoluminescence half width and the calculated alloy broadening showed high composition homo geneity for samples with low sulphur and magnesium contents (x, y 0.16 ) and poor homogeneity for samples with large x and y. Scanning transm ission electron microscopy investigations showed a low density of stru ctural defects in samples with narrow bandedge emission and low x and y, whereas a high defect density was detected in samples with large ba ndedge broadening. These results are correlated to the observation of symmetric and asymmetric profile shapes of the broadened X-ray rocking curves, respectively. Four-mode behaviour of the ZnMgSSe lattice vibr ations was testified by Raman measurements.