Effect of the lateral misalignment of Si-capped Ge quantum dots on the strain distribution, the valence, conduction states and the optical properties

We study the influence of the alignment of Si-capped Ge quantum dots to the strain distribution in the Si region, the electronic band states and the optical properties close to the fundamental gap. The study is performed on atomistic modelled structures, relaxed using simulated annealing and the electronic properties are determined by applying an accurate empirical tight-binding formulation within the complete three-center representation, considering interactions up to the third shell of neighbors. With this atomistic modelling we find that the top of the valence electronic states are not influenced much by the misalignment while the conduction states wavefunctions are greatly affected. In addition the strains present in the Si region augment the effect of the confining potential mainly by changing the shape of the wavefunctions. At the same time a comparison of these properties of quantum dots with stoichiometrically equivalent Si embedded Ge nanowires shows that there is similarity to a high degree.