Temperature dependence of the optical properties of CdTe

Abstract

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 ${\mathrm{N}}_2$ constantly flowed to minimize surface contamination. The spectral data revealed distinctive critical-point structures at $E_0$, $E_0+{\Delta }_0$, $E_1$, $E_1+{\Delta }_1$, $E_2\mathrm{}\left(X\right)\mathrm{}$, and $E_2\left(\Sigma \right)$. The spectral data were modeled. This enabled us to obtain the temperature dependence of the critical-point energies and linewidths. $E_0$, $E_0+{\Delta }_0$, $E_1$, $E_1+{\Delta }_1$, $E_2\mathrm{}\left(X\right)\mathrm{}$, and $E_2\left(\Sigma \right)$ 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.