Effects of elastic anisotropy on the self-organized ordering of quantum dot superlattices

Abstract

The vertical and lateral ordering of quantum dot superlattices is dependent on the elastic stress/strain fields induced by the buried quantum dots within the previous superlattice layers. It has been found that quantum dots may be vertically correlated or may exhibit anti-correlation for different material systems. These differences are caused by the elastic anisotropy as well as the crystallographic orientation of the materials. The finite element method is used in this work to investigate the effects of anisotropy of the elastic property and crystal orientation on the elastostatic fields of quantum dot superlattices. The strain energy density distribution obtained from the calculations can be used to deduce the locations whereby subsequent quantum dot islands will nucleate by locating the minima positions. A tetragonal body centred arrangement is observed for the CdSe/ZnSe(001) system with a sufficiently thick spacer layer. Through comparison with a less anisotropic system (InAs/GaAs), it is shown that an increase in the degree of anisotropy favours an anti-correlated island growth. Spatial correlation in different crystal orientations is also investigated and discussed.