Optical Properties of Plastically Deformed Germanium

$N$-type germanium specimens of 1 ohm-cm resistivity were plastically deformed from 3 to 15 percent at about 700°C. The more strongly deformed specimens were found to be converted to $p$-type. All of the deformed specimens exhibited a shift in the intrinsic absorption edge as well as an extended tail. Those samples which were converted to $p$-type also exhibit the characteristic absorption bands due to free holes. These results differ from those obtained for neutron-bombarded germanium which exhibits no shift of the absorption band and a tail of somewhat different character from that found in the plastically deformed material.