Mechanisms of strain relaxation in III-V semiconductor heterostructures

The known models describing the breakdown of coherency between layer and substrate in mismatched heterostructures are based on the isotropic elastic continuum approximation. As a matter of fact an internal contribution to the misfit accommodation, that is a deviation from the so-called “virtual crystal approximation”, is expected in ternary or more complex alloy structures. This effect is clearly seen in a set of In x Ga 1− x As / GaAs low misfit samples in the presence of misfit dislocations. The complete structural characterisation including the elastic distortion field and the dislocation density and distribution has been performed by means of Rutherford backscattering based techniques and double crystal X-ray diffraction.