Determination of critical layer thickness and strain tensor in InxGa1−xAs/GaAs quantum-well structures by x-ray diffraction

We have used the double-crystal x-ray rocking curve technique to determine lattice constant, strain relaxation, thickness, and critical thickness of a thin InxGa1−xAs layer embedded in GaAs. In this work we have measured and analyzed x-ray data over a wide scan angle (∼2.0°). This allows the simultaneous determination of buried layer thickness and strain. The measurement results were analyzed by the dynamical diffraction theory. The critical thickness for an InGaAs layer embedded in GaAs obtained from x-ray data is shown to be larger than that predicted by the force balance model. The strain tensors as a function of layer thickness are also analyzed for the buried InxGa1−xAs of different x values.