Anisotropic strain estimated from lattice parameters measured by bond method using X-ray diffraction, in molecular beam epitaxy-grown GaAs/Si(001)

x-, y- and z-components of lattice parameters on GaAs in GaAs films grown on Si(001) substrates by molecular-beam epitaxy have been experimentally measured from (004), (115) and (404) diffractions of GaAs by the Bond method using X-ray diffraction (XRD). The anisotropic strain on GaAs is estimated from the difference in each component of lattice parameters between the film and the GaAs bulk crystal. In-plane components of mechanical stress on GaAs are estimated from the measurement of substrate curvature using double-crystal XRD. The elastic strain is also estimated from the stress, assuming an elastic distortion of the lattice. However, it does not coincide with the strain derived from lattice parameters. The difference in the strain estimated by the two methods is largely especially near the interface, indicating strong, anisotropic and plastic deformation of the lattice, so that it can no longer be regarded as an elastic body. It is probably caused by lattice and stress relaxation related to the anisotropy of dislocations in the film.