Vertical and lateral ordering in self-organized quantum dot superlattices

The formation of vertically and laterally ordered dot superstructures in self-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 nucleation. For various materials systems, different types of ordered structures have been observed, ranging from vertically aligned dot superlattices for Si/Ge or III–V semiconductors to a fcc-like ABCABC… stacking in IV–VI materials. It is shown that the elastic anisotropy of the spacer material plays a crucial role in this self-organization process. In particular, for materials with very high elastic anisotropy and growth orientations parallel to an elastically soft direction, layer-to-layer dot correlations inclined to the growth direction can be formed. This is shown to be particularly effective 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.