Atomic-scale mapping of local lattice distortions in highly strained coherent islands of InXGa1-XAs/GaAs by high-resolution electron microscopy and image processing

During the epitaxy of highly strained InXGa1-XAs (x> 0.25) on {100}- oriented GaAs, a two-dimensional (2D)-three-dimensional transition of the growth mode was observed with formation of coherent islands. Deformations at the atomic scale were measured by image processing of high-resolution electron microscopy {110} projections. Quantitative experimental 2D contour maps of epsilon x and epsilon z deformations perpendicular and parallel respectively to the growth direction of the heterostructure, are presented. Experimental values are compared with theoretical calculations according to a model of homogeneous solid in biaxial compression. Indium segregation in both x and z directions was tentatively inferred.