Lattice curvature of InxGa1-xAs/GaAs [001] graded buffer layers

Ion channeling analysis and x-ray diffraction reciprocal space maps have been performed on InxGa1-xAs buffer layers grown with different composition profiles on well-cut (001) GaAs substrates. On all of the samples analyzed we detect a curvature of the layer lattice, i.e., a tilt of the lattice with respect to the substrate which varies coherently along the sample surface. The layer tilt is directed inward defining a curvature that is concave, large (up to 2.5 degrees cm(-1)) and that decreases when approaching the substrate. We describe this new phenomenon in terms of a coherent lateral distribution of the orientations of the misfit dislocation Burgers' vectors.