Funct. Mater. 2025; 32 (2): 184-189.

IR absorption spectra for n-Ge and n-Si single crystals, irradiated by fast electron flows, were investigated at room temperature. Additional absorption bands in the long-wave IR range, which are associated with the created radiation defects, were identified in these spectra after irradiation. In particular, in germanium: the absorption band at 15 µm for the VO_iI2Ge complex (vacancy-oxygen complex, two interstitial germanium atoms); in silicon: the absorption band at 12 µm for the A-center (vacancy-interstitial oxygen atom complex) and the A-center, modified by the phosphorus impurity (VO_iP complex), and the absorption band at 11.6 µm, which is associated with the C_iO_i complex (interstitial carbon-oxygen). The analysis of absorption spectra for the irradiated germanium and silicon single crystals and the calculations of the relative values of the photosensitivity coefficients for the obtained absorption bands show that the photosensitivity of these single crystals in the long-wave range of IR radiation increases with increasing the electron irradiation flow. This is due to an increase in the concentration of created radiation defects, which are absorption centres for IR radiation and, accordingly, determine the value of the photosensitivity coefficient. Electron-irradiated n-Ge and n-Si single crystals can be alternative materials to much more expensive and "cooled" narrow-gap semiconductor materials which are used in the devices controlling long-wave IR radiation.