Quantum Dots Formed by Ultrathin CdSe-ZnSe Insertions

We review on experimental and theoretical studies on a new type of quantum dot QD structures obtained growing ultrathin. i.e. below the critical thickness for 2D-3D transition. strained narrow gap insertions. The formation of dense arrays up to 10exp12cm2 of nanoscale two-dimensional islands formed by submonolayer SML or slightly above 1-ML CdSe insertions in a wide gap II-VI matrices is revealed in processed high-resolution transmission electron microscopy images. In the case of stacked sheets of SML insertions. the islands in the neighboring sheets are formed predominantly in correlated or anticorrelated way for thinner and thicker spacer layers respectively. By monitoring of sharp lines due to single QDs using cathodoluminescence the 3D confinement is confirmed. We manifest significant squeezing of the QD exciton wave function due to lateral confinement in magnetooptical experiments. Different polarization of photoluminescence PL emission recorded in edge geometry for vertically-uncoupled and coupled QDs confirms the QD nature of excitons. We show complete suppression of lateral motion of excitons bound to islands in case of wide-gap ZnMgSSe matrices.