Diffuse scattering in partially ordered III-V semiconductor alloys

Features of diffuse scatterings in III-V semiconductor alloys grown on a (001) substrate have been investigated by Monte Carlo simulation, on the basis of a simple kinetic Ising model we proposed previously. Atomic arrangements and their Fourier power spectra were compared with previous experimental results reported by other researchers. An epilayer includes numerous (001) plane faults and platelike CuPt(L11)-type ordered phases perpendicular to the growth direction. They give rise to the streaks along the [001] direction in an electron diffraction pattern. Our simulated result shows that the existence of like-atom clusters among the ordered domains causes the diffuse streaks drawn toward the fundamental lattice spots of a zinc-blende structure. With the progress of ordering, the wavy streaks become straightlike in shape and the position of their intensity maximum shifts from the -(1/2-δ), 1/2-δ,0 (δ>0) to the 1̄/21/21/2 in the reciprocal lattice space. The results obtained here have explained quite well some characteristic features of the CuPt ordering in epilayers revealed by experiments. We also discussed the ordering process during the epitaxial growth by using Warren-Cowley parameters.