Ion beam analysis of mismatched epitaxial heterostructures

The structural characterization of mismatched epitaxial heterostructures requires at least the determination of the strain and of the dislocation density. In this paper it is shown that ion-channeling is a very suitable technique for measuring both of these properties. In particular an improved technique for measuring the absolute angular distance between any crystal direction is presented. It is shown that in the case of single layer heterostructures the achieved precision is comparable to or better than that of double crystal X-ray diffraction. Moreover by computing the lattice distortion caused by a misfit dislocation the dechanneling cross section and its dependence from the relative orientation of the channeling and the dislocation directions have been evaluated. The application of these techniques for studying the mechanisms of strain relaxation in the InxGa1-xAs/GaAs system is presented.