Temperature dependence of the optical properties of silicon

The spectral dependence of the absorption coefficient of silicon for photon energies up to 2.7 eV was determined for several temperatures in the range 298–473 K. The effect of a temperature increase appears as a red shift of the absorption spectrum. The magnitude of the shift is larger than that of the fundamental energy gap, increases with increasing photon energy in the range 1.1–1.7 eV, and is constant for energies greater than 1.7 eV. A phenomenological expression deduced by analysis of the data may be used to calculate α (E) at elevated temperature, given α (E) at room temperature. The reflectance was also measured at 299, 413, and 516 K in the photon energy range 2.5–3.8 eV.