Mixing enthalpy and composition fluctuations in ternary III–V semiconductor alloys

Abstract

The mixing enthalpy of ternary tetrahedral semiconductor alloys is fairly well described by regular solution theory, with a thermodynamic interaction parameter that is sensitive to the lattice spacing of the binary constituents. We derive an estimate of the interaction parameter from a model which ascribes the mixing enthalpy to bond distortions associated with the alloy formation, and relates these to the macroscopic elastic properties of the crystal. Numerical estimates are given for the 18 alloys with cations Al, Ga, In and anions P, As, Sb and are compared with experimental values and alternative models. To within a single adjustable parameter, the predictions agree with experiment and are consistent with those of the delta lattice parameter (DLP) model. A further calculation of the elastic energy associated with composition fluctuations (clustering) in these alloys indicates that this energy is sufficient to suppress clustering above the critical mixing temperature.