Vertical and lateral ordering in self-organized quantum dot superlattices

The formation of vertically and laterally ordered dot superstructures in se lf-organized quantum dot superlattices is described. The ordering is based on the long-range elastic interactions between the strained self-assembled quantum dots, providing a driving force for a spatially correlated dot nucl eation. For various materials systems, different types of ordered structure s have been observed, ranging from vertically aligned dot superlattices for Si/Ge or III-V semiconductors to a fee-like ABCABC... stacking in IV-VI ma terials. It is shown that the elastic anisotropy of the spacer material pla ys a crucial role in this self-organization process. In particular, for mat erials with very high elastic anisotropy and growth orientations parallel t o an elastically soft direction, layer-to-layer dot correlations inclined t o the growth direction can be formed. This is shown to he particularly effe ctive for inducing a lateral ordering of the dots within the growth plane, which can lead to a significant narrowing of the dot size dispersion. These conclusions are also supported by Monte Carlo growth simulations. (C) 2001 Elsevier Science B.V. All rights reserved.