Diffuse X-ray scattering study of sublattice ordering among Group III atoms in In_0.5Ga_0.5P and In_0.5Al_0.5P

The intensity of superstructure reflections and associated diffuse scattering from In_0.5Ga_0.5P and In_0.5Al_0.5P epitaxic layers grown on (001) GaAs substrates was mapped in reciprocal space. The Warren-Cowley short-range-order parameters were obtained through the usual process for evaluating Fourier coefficients. Varying values for the correlation length in different directions indicate how group III atoms stack up in ordered states. The resultant structure with long-range order confirms the hypothesis made on the basis of electron diffraction and high-resolution transmission electron microscopy studies.