Tuning the configuration of quantum dot molecules grown on stacked multilayers of heteroepitaxial islands

Abstract

Arrays of Ge quantum dot molecules were grown by molecular beam epitaxy using a template, composed of a multilayer structure with layers of vertically aligned three-dimensional (3D) Ge islands buried in an Si crystal matrix with the Si capping layer on top. Depending on preparation conditions, the molecules assume various configurations, including a square frame with [001]–[010]-oriented sides. It was shown by scanning tunneling microscopy that the 3D islands are located closer to the buried SiGe mound centers with the increase of the capping layer thickness. The mechanism of the quantum dot molecule formation is ascribed to strain relaxation. It was confirmed by Monte Carlo simulations of heteroepitaxial Ge growth on the template, containing the buried Ge mound.