Nominally binary CdSe quantum wells with thicknesses ranging from 1 to 2.5 monolayers, embedded in ZnSe, were grown onto GaAs(001) by means of molecular beam epitaxy. Investigation of the samples by means of high-resolution X-ray diffraction and high-resolution transmission electron microscopy was focussed on the vertical Cd distribution in the quantum-well region. Both the total Cd content and the real quantum-well thicknesses, as determined by using the above methods, were in good agreement. The results indicated the formation of ternary ZnCdSe wells, having thicknesses of 4 to 6 monolayers, which were almost independent of the intended quantum-well thickness and the substrate temperature during growth. This was attributed to strongly enhanced Cd diffusion in ZnSe, or to Cd surface segregation.

Analysis of Cadmium Diffusion in ZnSe by X-Ray Diffraction and Transmission Electron Microscopy. H.Heinke, T.Passow, A.Stockmann, H.Selke, K.Leonardi, D.Hommel: Journal of Crystal Growth, 2000, 214-215, 585-9