Planar dechannelling by networks of misfit dislocations was studied in a series of InGaAs on (001) GaAs samples which had been grown by means of molecular-beam epitaxy. At the beginning of the strain-relaxation process, the dechannelling probability exhibited differing values for nominally equivalent (110) planes. At larger strain relaxations, the dechannelling probability saturated at a value near to unity as the beam-energy increased. A new model for planar dechannelling by dislocations was proposed in order to explain the results. The model was based upon an harmonic approximation of the continuum potential, but anharmonicity effects were taken into account. The perturbation of harmonic oscillations, caused by the lattice-plane curvature around a dislocation, was expressed in terms of a distortion function that depended only upon the geometrical configuration of the channelling direction and of the dislocation line. This function was calculated explicitly for geometrical configurations that were relevant to the present samples; thus permitting solution of the equation of motion. The results showed that the dechannelling probability saturated at a level which was appreciably lower than 100%, due to the quasi-planar dislocation distribution. A comparison of calculated and measured dechannelling probabilities predicted dislocation densities that were in excellent agreement with those measured using transmission electron microscopy, without invoking any adjustable parameter. The predictions were also in good agreement with the results of published strain-relaxation data.

M.Mazzer, A.V.Drigo, F.Romanato, G.Salviati, L.Lazzarini: Physical Review B, 1997, 56[11], 6895-910