Self-organized ordering in self-assembled quantum dot superlattices

Self-organized vertical and lateral ordering in self-assembled quantum dot superlattices is based on long-range elastic interactions between the growing dots on the surface and those buried in the previous superlattice layers. These interactions may lead to a correlated dot nucleation and to the formation of ordered superstructures. For various materials systems different types of structures may be formed, ranging from vertically aligned dot superlattices for Si–Ge or III–V semiconductors to an fcc-like ABCABC… stacking in IV–VI materials. These differences are caused by the given elastic anisotropy of the superlattice materials. From systematic theoretical calculations, for all materials with high elastic anisotropy and growth orientations parallel to an elastically soft direction, layer-to-layer dot correlations inclined to the growth direction may be formed. Further changes in the dot correlations are caused by the modification of the elastic strain fields by the finite extent and shape of the buried islands. This is illustrated for IV–VI PbSe/PbEuTe dot superlattices, where either vertically aligned or fcc-stacked dot arrangements are formed as a function of spacer thickness.