Structural and optical evidence of island correlation in CdTe/ZnTe superlattices

The properties of superlattices consisting of 2 monolayer wide CdTe inserti ons into ZnTe spacer barriers with thickness ranging from 3 to 75 monolayer s are investigated by means of transmission electron microscopy and photolu minescence spectroscopy We show that quasi zero-dimensional CdTe islands fo rm in this highly lattice-mismatched system. For spacer thickness smaller t han 25 monolayers, the islands are vertically correlated along the axis til ted by 40 degrees with respect to the growth direction, while for thicker Z nTe spacers no con-elation is observed. The electronic coupling between the correlated islands manifests itself by the appearing of an additional emis sion band at energies lower to those corresponding to uncorrelated dots. Th e optical spectrocopy data reveal zero-dimensional localization of excitons by the electronically coupled islands. The decay time of the excitonic rec ombination is found to be over an order of magnitude longer in the case of the coupled islands than in the case of isolated ones. (C) 2001 American In stitute of Physics.