Determination of optical constants for cubic InxGa1-xN layers

Spectroscopic ellipsometry studies have been carried out in the energy range from 1.5 to 4.0 eV in order to determine the complex refractive indices for cubic InGaN layers with various In contents. Studying single GaN films we prove that for the analysis of optical data a parametric dielectric function model can be used. Its application to the InGaN layers yields the refractive index and extinction coefficient as function of photon energy as well as the compositional dependence of the fundamental absorption edge at room temperature. From the latter a bowing parameter of 1.4 eV is deduced.