Anisotropy of the spatial distribution of In(Ga)As quantum dots in In(Ga)As-GaAs multilayer heterostructures studied by x-ray and synchrotron diffraction and transmission electron microscopy

High-resolution X-ray and synchrotron (crystal truncation rods) diffraction methods and transmission electron microscopy have been employed to study M BE-grown multilayer In(Ga)As-GaAs heterostructures with arrays of verticall y coupled In(Ga)As quantum dots (QDs) in a GaAs matrix. Additional (vertica l and lateral) spatial ordering of QDs in perfect crystalline structures, g iving rise to undulations of the crystalline planes and quasi-periodic elas tic strain, was shown to be essentially anisotropic with respect to crystal lographic directions of the [110] type. The anisotropy of the QD formationa l system of can be accounted for by assuming that the spatial ordering of t he QDs and the corrugation of the crystal planes are the initial stages of relaxation of the elastic strain introduced into the system by the QDs. The anisotropic relief of the crystal planes (corrugated growth surface) resul ts from the formation of a system of spatially ordered quantum quasi-wires uniformly filled with QDs. In a multilayer heterostructure with high crysta l perfection, the anisotropic relief of the crystal planes is inherited by overlying layers and its amplitude decreases gradually with increasing dist ance from the source of elastic strain-the superstructure containing In(Ga) As QDs in the given case. (C) 2001 MAIK "Nauka/Interperiodica".