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

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 0C) using polarization modulation ellipsometry. For photon energies below approx.3 eV (approx.410 nm), the absorption coefficient increases exponentially with temperature from room 240 C to 700 0C, 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