Morphology of ultrathin CdSe quantum confinement layers in ZnSe matrices

Using a combination of transmission electron microscopy (TEM). high resolut ion TEM (HRTEM), digital analysis of lattice images (DALI), and corresponde nce analysis (CA) we present at near-atomic resolution the morphology of a nominal 2 monolayer (ML) cadmium selenide (CdSe) quantum well (QW) between ZnSe barriers. We reveal the presence of similar to 10 hit zinc cadmium sel enide (ZnxCd1-xSe) alloy insertion layer of varying composition in a ZnSe m atrix, A spotty pattern in the plane of the layer indicates the presence of self-assembled clusters or islands similar to the structures commonly refe rred to as quantum dots. Further analysis indicates that these clusters, of less than 10 nm in lateral extent, themselves contain sites highly saturat ed with CdSe. Analysis of photoluminescence (PL) spectra suggests that the emission originates predominantly from excitons trapped in these islands. ( C) 1999 Elsevier Science B.V. All rights reserved.