Parameterization of the optical functions of amorphous materials in the interband region

A parameterization of the optical functions of amorphous semiconductors and insulators is presented in which the imaginary part of the dielectric function ε2 is determined by multiplying the Tauc joint density of states by the ε2 obtained from the Lorentz oscillator model. The real part of the dielectric function ε1 is calculated from ε2 using Kramers–Kronig integration. The parameters of this model are fit to n and k data for amorphous Si (2 data sets), SiO, As2S3, and Si3N4. Comparative fits are made with a similar parameterization presented earlier by Forouhi and Bloomer Phys. Rev. B 34, 7018 (1986). In all cases, the new parameterization fits the data better.