In a previous paper, the authors proposed a model for the optical dielectric function of zinc-blende semiconductors. It was found to be more generally valid than previous models. In this paper, it is used to obtain an analytic expression for the dielectric function of the alloy series ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As as a function of ω and x, which is compared with spectroscopic ellipsometry data between 1.5 and 6.0 eV. The model enables us to determine accurately the critical point energies and linewidths of ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As as a function of x. Also, it leads us to model the optical dielectric function of these alloys better than any previous model in that (1) it covers the entire photon energy range between 1.5 and 6.0 eV as well as the entire alloy composition range between 0.0 and 1.0, (2) it calculates the optical properties of ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As as a function of ω and x with the highest accuracy, and (3) it allows one to accurately calculate the values of the refractive indices below 1.5 eV as a function of ω and x.

• Received 27 August 1992

DOI:https://doi.org/10.1103/PhysRevB.47.1876