Optical constants for silicon at 300 and 10 K determined from 1.64 to 4.73 eV by ellipsometry

Abstract

Polarization modulation ellipsometry has been used to determine the optical constants of Si for photon energies from 1.64 to 4.73 eV (755 to 262 nm) at 300 as well as 10 K. The results were interpreted using a 2-boundary, 3-layer model (air-SiO2-Si); the inclusion of an interface layer between the SiO2 and Si did not greatly affect the derived optical constants below ∼3.5 eV. The accuracy of the results has been carefully evaluated, the error in the index of refraction (n) being < 1%, while the error in the extinction coefficient (k) or the absorption coefficient (α) being dependent upon the magnitude, ∼15% at α = 104 cm−1, ∼6% at α = 105 cm−1, and ∼1.5% at α = 106 cm−1. The room temperature absorption coefficient results represent the best spectroscopically available values from ∼2.5 to ∼3.5 eV (∼350 to 500 nm), while results at 10 K represent the best values available over the entire wavelength region measured. A comparison with previously published data is presented.