X-ray analysis of the short-range order in the ordered-alloy domains of epitaxial (Ga,In)P layers by diffraction anomalous fine structure of superlattice reflections

Ordered-alloy domains of epitaxially grown (Ga,In)P layers have been observed elsewhere using transmission electron microscopy and transmission electron diffraction. We used diffraction anomalous fine-structure (DAFS) experiments at superlattice reflections occurring in several $〈111〉$ directions to explore the short-range order around Ga atoms in such ordered domains in epitaxial (Ga,In)P layers grown on (001) GaAs substrates. The requirements for a reliable measurement of the reflection intensity depending on the photon energy are described. A quantitative DAFS analysis resulting in short-range order parameters is explained in detail. The local structure around Ga in the whole (Ga,In)P layer (F43m) can be understood by a local structure model, while contrary to that the local structure around Ga atoms in the ordered regions $(R3m)$ can be described by the values expected on the basis of the virtual-crystal model.