Temperature dependence of the optical properties of CdTe

CdTe(111)B films were grown on Si(100) substrates by molecular-beam epitaxy. Their spectral data were obtained from room temperature to 800 K by spectroscopic ellipsometry (SE) in the photon energy range from 1.3 eV to 6 eV. During the measurement, samples were heated inside a windowless chamber in which high-purity N₂ constantly flowed to minimize surface contamination. The spectral data revealed distinctive critical-point structures at E₀, E₀+Δ₀, E₁, E₁+Δ₁, E₂(X), and E₂(Σ). The spectral data were modeled. This enabled us to obtain the temperature dependence of the critical-point energies and linewidths. E₀, E₀+Δ₀, E₁, E₁+Δ₁, E₂(X), and E₂(Σ) decreased at the rate of 0.37, 0.34, 0.82, 0.64, 0.92, and 0.45 meV/K, respectively. All linewidths monotonically increased. The optical dielectric function was expressed as a function of temperature within and outside the experimental range. The results can be utilized for thermometry in order to determine the temperature of sample surfaces during growth.