Heterostructures with ultrathin InxGa1−xAs/GaAs (001) metamorphic buffer layers and InAs/InGaAs QDs grown by molecular beam epitaxy

The heterostructures with ultrathin (~220 nm) In_xGa_1-xAs/GaAs (001) metamorphic buffer layers with a convex indium composition profile were grown by molecular beam epitaxy and studied using structural characterization techniques. Analysis of atomic force microscopy images revealed a relationship between the surface roughness and the growth conditions of the graded layer. The density of threading dislocations in the structures with a ultra-thin graded layer was estimated as ~107 cm^-2, which is consistent with the high average grading rate of ~90% In/μm. The reciprocal space maps of high-resolution X-ray diffraction measured for both symmetric (004) and asymmetric (224) reflections in grazing exit geometry are presented.