Configurational atomic ordering caused by stochastic adsorption processes in MBE-grown alloy semiconductors

The recently observed atomic long-range ordering (LRO) phenomenon in epitaxial alloy semiconductors suggests the possibility to control these atomic arrangements artificially. It is promising in the sense that we can design the energy-band structures of alloy semiconductors and eliminate the effects of alloy scattering in the carrier mobilities. However, it is necessary to understand the mechanism which determines the atomic arrangements of alloy semiconductors grown through the dynamic epitaxial growth processes. In this paper, the dynamic atom-incorporation process in MBE is modeled using a concept of “site-correlated adsorption probabilities” within the framework of the dynamic three-dimensional Ising model. The adsorption probabilities are defined, with the local equilibrium approximation, in terms of intralayer interatomic interaction parameters as well as interlayer interatomic interaction parameters. The intralayer (in-plane) interatomic interaction is influenced by surface atomic dimers, which induce the anisotropy in interatomic interaction parameters between the atomic bonds in the dimer-bond direction and the atomic bonds in the normal direction. It has been found that partial LROs such as L10 (CuAu-I), L11 (CuPt) and E11 (chalcopyrite) can be caused by dynamic site-correlated adsorption processes. It is also found that the type of LRO is classified and predictable by the types of interatomic interaction.