Infrared Absorption and Photoconductivity in Irradiated Silicon

Abstract

The effects of irradiation on the infrared absorption and photoconductivity in silicon are reported. The absorption near the intrinsic edge is increased and drops off more gradually toward longer wavelengths. Several absorption bands are introduced by neutron irradiation with peak absorptions at 1.8, 3.3, 3.9, 5.5, and 6.0 μ, respectively. The observation of each band depends upon the position of the Fermi level. The 1.8‐μ band has also been studied for deuteron irradiated and electron irradiatedsilicon, and the 3.3‐μ band has been observed in electron irradiated samples. The absorption bands arise from electronic excitations of various types of defects and associated photoconductivity has been observed for the 3.9‐μ and 5.5‐μ bands. In addition absorption bands have been observed at long wavelengths: 20.5, 27.0, and 30.1 μ, which are associated with lattice vibration. The significance of these results is discussed.