Superstructured ordering in Al$_x$Ga$_{1-x}$As and Ga$_x$In$_{1-x}$P alloys

Epitaxial heterostructures produced on the basis of Al$_x$Ga$_{1-x}$As and Ga$_x$In$_{1-x}$P ternary alloys by metal-organic chemical vapor deposition are studied. The composition parameter x of the alloys was $\sim$ 0.50. By X-ray diffraction studies, scanning electron microscopy, atomic force microscopy, and photoluminescence spectroscopy, it is shown that superstructured ordered phases with the stoichiometry composition III$_{1-\eta}$III$_{1+\eta}$V$_2$ can be formed. As a consequence of this effect, not only does the cubic crystal symmetry change to the tetragonal type in the new compound, but also the optical properties become different from those of disordered alloy with the same composition.