Investigation of the temperature dependence of the spectra of optical constants of Hg$_{1-x}$Cd$_{x}$Te films grown using molecular beam epitaxy

Based on in situ and ex situ ellipsometric measurements, the spectral dependences of the temperature sensitivity of the optical constants Hg$_{1-x}$Cd$_{x}$Te – $dn(\lambda)$ and $dk(\lambda)$ have been found for a series of samples of different compositions in the range from 0.160 to 0.327. The experiments were performed during cooling of the grown samples in a vacuum chamber. It has been found that the obtained $dn$ and $dk$ dependences can be well approximated by the sum of three Lorentz oscillators with the addition of the dispersion terms of the Cauchy formula. A parametric model that describes the sensitivities $dn(\lambda)$ and $dk(\lambda)$ for an arbitrary composition $x$ in the specified range near the growth temperature has been proposed. Ex situ temperature measurements performed near room temperature correlate with the data of the high-temperature measurements. The results obtained are relevant for the development of ellipsometric control methods in situ of Hg$_{1-x}$Cd$_{x}$Te layer growth processes.