Optical absorption of silicon between 1.6 and 4.7 eV at elevated temperatures

Abstract

The optical absorption coefficient of silicon for photon energies between 1.65 and 4.77 eV (750- 260 nm) has been determined at elevated temperatures (up to 700°C) using polarization modulation ellipsometry. For photon energies below ∼3 eV (∼410 nm), the absorption coefficient increases exponentially with temperature from room 24°C to 700°C, increasing by a factor of approximately 5 over that temperature range. The threshold for direct band-gap absorption moves to lower energies with increasing temperature.