Measurement of aluminum concentration in epitaxial layers of AlxGa1−xAs on GaAs by double axis x-ray diffractometry

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Abstract
The composition of a series of AlxGa1−xAs layers grown epitaxially by molecular beam epitaxy (MBE) on GaAs has been measured independently by double axis x‐ray diffractometry and reflection high‐energy electron diffraction. From a quadratic fit to the data, we deduce the lattice parameter mismatch between AlAs and GaAs and the Poisson ratio of AlAs. Asymmetric reflection rocking curves and synchrotron x‐ray topography have been used to show that the anomalously low substrate‐layer peak splitting for the 1‐μm‐thick AlAs layer results from relaxation, which is asymmetric. Use of the AlAs rocking curve peak splitting corrected for relaxation yields a mismatch of 1600 ppm (±1%) between AlAs and GaAs, and 0.28±0.01 for the Poisson ratio of AlAs.