Characterization of (In,Ga,Al)As/GaAs quantum-dot superlattice structures by high-resolution X-ray diffraction

High-resolution X-ray diffraction measurements have been performed on (In,G a,AI)As/GaAs quantum-dot superlattice structures. We are able to observe up to 31 satellite peaks from 6 periods of a quantum-dot superlattice. Theore tical simulations of the rocking curves based on the Takagi-Taupin equation s of dynamical diffraction theory agree well with the experimental data. It is found, however, that to obtain agreement between theory and experiment, the height of the quantum dot, including the wetting layer under the dot, must be used in the simulations; furthermore, the indium composition is app arently reduced from its nominal value. Our results appear to support the n otion that for the (In,Ga,Al)As materials system, the dots play an importan t role in contributing to the diffraction signature from the superlattice s tructure. (C) 2001 Elsevier Science B.V. All rights reserved.