Elastic distortion field in single layer heterostructures in the presence of misfit dislocations

Abstract

The elastic distortion field in (001)-grown lattice mismatched heterostructures of diamond or zinc-blende structure having misfit dislocations at the interface is calculated within the linear elasticity theory. Not only the misfit dislocation densities in the two 〈110〉 directions but also the distribution of the possible Burgers vectors are taken into consideration. A transition layer where the elastic field is appreciably laterally nonuniform extends from the interface up to a distance of the same order of the mean dislocation spacing. It is shown that this transition layer affects x-ray diffraction measurements. Beyond this region, the elastic distortion field is uniform and is found to depend only on the mean values of the Burgers vectors associated with the two dislocation distributions. In particular it is shown that in general the strain field, i.e., the symmetric part of the elastic distortion field, is not biaxial. The three independent parameters describing the lattice deformations in the epilayer depend not only on the projections on the interface of the edge components but also on the screw components of the Burgers vectors. The predictions of this model are tested on InxGa1−xAs/GaAs samples analyzed by means of channeling and double crystal x-ray diffractometry. The unbalance of the dislocation densities in the two 〈110〉 directions measured by the dechanneling behavior of the samples agrees rather well with the prediction of the model on the basis of the measured asymmetries of the strain field.