High resolution x-ray diffraction and reflectivity studies of vertical and lateral ordering in multiple self-organized InGaAs quantum dots

We have investigated multiple layers of self-assembled InGaAs quantum dots by high-resolution X-ray diffraction reciprocal space mapping and reflectivity. An anisotropy in the dot spacing was found, which proves an ordering of the islands in a disordered two-dimensional square lattice with main axes parallel to the direction and a lateral lattice parameter of 55 nm. Vertical correlations in the dot multilayers were investigated nondestructively in the regime of total external reflection of X-rays.