STRUCTURAL CHARACTERIZATION OF SELF-ASSEMBLED QUANTUM-DOT STRUCTURES BY X-RAY-DIFFRACTION TECHNIQUES

We have investigated, by means of X-ray diffraction reciprocal space m apping and X-ray reflectivity, multilayers of self-organized InGaAs qu antum dots grown on GaAs by MBE. An anisotropy of the average inter-do t spacings in the [100] and [110] directions was found, consistent wit h an ordering of the dots in a two-dimensional square lattice with mai n axes along the <100>-directions and a lattice parameter of 55 nm. Th e nearly perfect vertical alignment (stacking) of the dots was deduced consistently from the diffraction peak shape and from measurements of the resonant diffuse scattering in the X-ray reflection regime. (C) 1 997 Elsevier Science S.A.