Three-dimensional stacking of self-assembled quantum dots in multilayer structures

Abstract

Three-dimensional stacking of semiconductor nano-islands in multilayers or superlattice structures provides a powerful tool for controlling the properties of self-assembled quantum dots. These stackings can be caused by several different mechanisms based on: (i) elastic interactions due to the strain fields of the buried dots; (ii) morphological interactions due to nonplanarized spacer topographies; or (iii) interactions based on chemical composition modulations within the spacer material. All three interactions may give rise to a vertical dot alignment in columns as well as to oblique or staggered dot stackings, depending on the details of the interaction mechanisms. For the interlayer correlations mediated by the elastic strain fields, the elastic anisotropy and surface orientation, but also the dot sizes and spacer layer thicknesses play a crucial role. As a result, transitions between different types of dot stackings can be induced as a function of spacer layer thicknesses and growth parameters. The large range of parameters involved in interlayer correlation formation may allow the controlled synthesis of new types of ordered structures with novel properties.