Monocrystals were grown under an applied magnetic field, and doping occurred due to the formation of Mg-related centers by transmutation reactions of 28Si and 29Si isotopes after irradiation with fast neutrons. Post-irradiation annealing at high temperatures led to the formation of shallow and deep donor centers. The separate micro-defects were not revealed by X-ray topography, and no striations which were related to the micro-defect distribution were observed. Far-infrared photoconductivity was observed at photon energies which were lower than the H-like ionization energy which was calculated using the effective mass approximation. The photoconductivity was associated with shallow donor centers that included Mg atoms.

T.Tkacheva, G.Petrov, E.Shabalin, V.Golubev, G.Kropotov, E.Shek, N.Sobolev: Materials Science Forum, 1995, 196-201, 1153-8