Self-organized growth of three-dimensional IV–VI semiconductor quantum dot crystals with fcc-like vertical stacking and tunable lattice constant

Heteroepitaxial growth of highly lattice-mismatched semiconductor layers has evolved as a novel method for direct synthesis of self-assembled quantum dots based on the Stranski–Krastanov growth mode. In this growth mode, nano-scale three-dimensional (3D) islands are spontaneously formed on the epitaxial surface once the layer thickness exceeds a certain critical coverage. In multilayer structures, the interaction of the strained islands via their long-range elastic strain fields may lead to a vertical and lateral ordering of the dots. Here, it is shown that the elastic anisotropy and the growth orientation play a crucial role for this self-organization process. In particular, for (111)-oriented IV–VI semiconductor (PbSe/Pb1−xEuxTe) multilayers, the direction of the interlayer dot correlations is shown to be inclined to the surface normal. This leads to a fcc-like ABCABC… vertical dot stacking sequence, which is particularly effective for inducting a lateral ordering of the dots as well. As a result, large domains of trigonally ordered 3D quantum dot crystals are formed, and their lattice constant can be tuned continuously just by changing the thickness of the spacer between the quantum dot layers.