Local structure of In_x Ga_{1 − x} As semiconductor alloys by high-energy synchrotron x-ray diffraction

Nearest- and higher-neighbor distances as well as bond length distributions (static and thermal) of the In_x Ga_{1 − x} As (0 < ∼ x < ∼ 1) semiconductor alloys have been obtained from high-real-space resolution atomic pair distribution functions. Using this structural information, we modeled the local atomic displacements in In_x Ga_{1 − x} As alloys. From a supercell model based on the Kirkwood potential, we obtained three-dimensional As and (In, Ga) ensemble average probability distributions. These clearly show that As atom displacements are highly directional and can be represented as a combination of ⟨ 100 ⟩ and ⟨ 111 ⟩ displacements. Examination of the Kirkwood model indicates that the standard deviation (σ) of the static disorder on the (In, Ga) sublattice is around 60% of the value on the As sublattice and the (In, Ga) atomic displacements are much more isotropic than those on the As sublattice. The single-crystal diffuse scattering calculated from the Kirkwood model shows that atomic displacements are most strongly correlated along ⟨ 110 ⟩ directions.