Influence of radiation damage on the absorption of near-infrared light in silicon

Abstract

The absorption length, ${\lambda }_{abs}$, of light with wavelengths between 0.95 and 1.30$\mu$m in silicon irradiated with 24 GeV/c protons to 1 MeV neutron equivalent fluences between 0 and $8.6\times 10^{15}$cm${}^{-2}$ has been measured. It is found that ${\lambda }_{abs}$ decreases with fluence due to radiation-induced defects. A phenomenological parametrisation of the radiation-induced change of ${\lambda }_{abs}$ as a function of wavelength and neutron equivalent fluence at room temperature is given. The observation of the decrease of ${\lambda }_{abs}$ with irradiation is confirmed by edge-TCT measurements on irradiated silicon strip detectors. Using the measured wavelength dependence of ${\lambda }_{abs}$, the change of the silicon band-gap with fluence is determined.