Optical functions of silicon at high temperatures

The optical spectra of silicon are studied ellipsometrically at temperatures between 300 and 1200 K in the spectral range from 2 to 4.3 eV. We present a database of optical constants for pure and heavily doped samples, with the highest concentration of free carriers of 4×1020 cm−3. We cover the photon energy range between 0.2 and 2 eV by using an oscillator representation of the visible and ultraviolet ellipsometric data. We also report the results for the temperature dependence of the E1 interband transition. The values of the energy shift and Lorentzian broadening of this spectral feature are obtained from analytical critical-point line shapes by fitting differentiated dielectric functions; alternatively, we apply the numerical convolution with Lorentzian contours to describe quantitatively the increased broadening with increasing temperature.