Diffraction anomalous near-edge structure in ordered GaInP

We report the diffraction anomalous near-edge structure (DANES) of a nominally lattice matched GaxIn1-xP/GaAs (x = 0.51) heteroepitaxial layer, grown by metal organic chemical vapor deposition, which shows long range ordering in the cationic sublattice along the ?111? direction. DANES spectra, originating from the 004 reflections of the substrate and of the epi-layer and that from the "forbidden" -5/2 5/2 -5/2 reflection of the superstructure, have been recorded at the Ga K edge. A full theoretical simulation, based on the kinematic formalism, largely agrees with the experimental data.