Optical properties of CdTe: Experiment and modeling

The optical response of CdTe in the 1.1–5.6 eV photon-energy range at room temperature has been studied by spectroscopic ellipsometry. The measured ε(E) data reveal distinct structures at energies of the E0, E1, E1+Δ1, and E2 critical points. These data are analyzed using various theoretical models, namely the model dielectric function (MDF), harmonic-oscillator approximation (HOA), and standard critical-point (SCP) model. Results are in satisfactory agreement with the MDF calculations over the entire range of the photon energies. The HOA (five oscillators) cannot successfully explain the peculiar experimental ε(E) data. The SCP model can provide satisfactory fits to the derivatives of ε(E), but does not yield good fits to ε(E). Dielectric-related optical constants of CdTe, such as the complex refractive index, the absorption coefficient, and the normal-incidence reflectivity, are presented and analyzed. Results of the chemical surface-treatment effect on the pseudodielectric functions have also been presented.