X-ray Diffraction on Laterally Modulated (InAs)n/(AlAs)m Short-Period Superlattices

Lateral composition modulation in InAs/AlAs short-period superlattices was investigated by x-ray grazing-incidence diffraction and coplanar x-ray diffraction at a "normal" wavelength and at an anomalous wavelength, for which diffraction from the (200) planes does not exhibit a chemical contrast. The experimental data were compared with theoretical simulations assuming that the interfaces consist of a periodic sequence of monoatomic steps. The displacement field in the superlattice was calculated by continuum elasticity and using a valence-force field method. From the fit of the experimental data to the theory, the lengths of individual atomic terraces were determined.