Radiation Effects on Recombination in Germanium

The properties of recombination centers in germanium are obtained on the basis of lifetime data in conjunction with other information available. For recombination centers introduced by Co60 gamma rays and fission neutrons, the recombination energy level position is placed at 0.20 ev below the conduction band. The room temperature hole-capture cross sections resulting are 1.1×10−15 cm2 and 6×10−15 cm2 for Co60 gammaray and fission neutron irradiation, respectively. For the case of 14-Mev neutron irradiation the energy level is located 0.32 ev above the valence band. The room temperature hole and electron cross sections are ∼6 ×10−15 cm2 and 2.2×10−17 cm2, respectively. The capture probabilities are assumed to be independent of temperature except for the case of gamma irradiation, for which there is apparently a fairly strong variation corresponding to a change in the activation energy of 0.07 ev. The selection of the values given above is not entirely unique. The assumptions made in their determination are discussed. The values given are directly applicable only in the case of n-type material, the situation in p-type material being more complex.