Study of strain relaxation in CdSe/ZnSe nanostructures

Strain relaxation in CdSe/ZnSe self-assembled quantum dot (QD) and CdZnSe/ZnSe quantum well (QW) structures have been investigated by the photoluminescence (PL) and high-resolution X-ray diffraction methods. The PL spectra of the QW structures revealed that splitting of free exciton line in ZnSe cap layer is influenced significantly by Cd content in QWs that allows to obtain information about strain in quantum-confinement structures. It is shown that information about strain relaxation mechanism and interdiffusion processes can be obtained from the analysis of the PL spectra of free and bound excitons. It is found that strain relaxation in the QD structures occurs mainly via QD formation in spite of generation of extended defects. Significant doping of ZnSe cap layer with Cd is found both in the QW and QD structures. The data obtained from the simulations of X-ray diffraction profiles qualitatively proved the results obtained from the analysis of ZnSe excitonic spectra. The reasons of quantitative discrepancy are discussed.