Studies of Recombination Centers in Gamma-Irradiated p-Type Silicon

抄録

Recombination centers produced by Co⁶⁰ γ-ray irradiation at room temperature were investigated by measuring the temperature dependence and the annealing behaviors of the minority carrier lifetime. Both isochronal and isothermal annealing of the lifetime at a fixed measurement-temperature were observed. The measurement at 150°K show that A-center at E_C−0.17 eV is the most effective recombination center about the region of this temperature in all p-type specimens. The first order annealing process with an activation energy of 1.27 eV was found in agreement with the values reported earlier. The capture cross section for electrons and holes were estimated to be 1.2×10⁻¹⁵ cm² and 1.8×10⁻¹⁴ cm², respectively. The introduction rate of inverse lifetime measured at 150°K seems to show that A center is introduced at nearly the same rate in both floating zone and pulled crystals. At and above room temperature the recombination center at ∼E_V+0.3 eV was found to control the lifetime. The annealing activation energy of this center was found to be dependent on the kind of impurities, and estimated to be 1.27 and 0.98 eV, in boron- or gallium-doped floating zone specimens, respectively. The reaction order of recovery process of this center was less than one. This center seems to be a complex defect containing a dopant impurity.