Radiation Effects and Their Annealing inCo60-Gamma-Irradiated Sb-Doped Germanium

The annealing of changes in the electrical properties of antimony-doped germanium caused by ${\mathrm{Co}}^{60}$ gamma irradiation at 77°K has been investigated by both isochronal and isothermal techniques. The previously observed levels at 0.2 eV below the conduction band and near or below the middle of the forbidden band were studied individually. It was found that both the rate of carrier removal and the subsequent course of recovery upon annealing above 273°K were markedly dependent upon the antimony concentration ($N_{\mathrm{Sb}}$). The rate of electron removal ($\frac{\mathrm{dn}}{d\phi t}$) is smaller for lower antimony concentrations. Upon annealing in the range between 273 and 450°K, two distinct stages are observed. Stage A accounts for the major recovery of the change in carrier concentration for samples with high antimony concentration ($N_{\mathrm{Sb}}={10}^{15}$ ${\mathrm{cm}}^{-3\mathrm{}}$) and for the major recovery of reciprocal mobility for both high- and low-purity material. By contrast, the major recovery of carrier concentration for the low antimony concentrations ($N_{\mathrm{Sb}}\approx {10}^{14}$ ${\mathrm{cm}}^{-3\mathrm{}}$) occurs in the high-temperature stage, stage B. Stage B proceeds with an apparent activation energy of ∼ 1.2 eV. The annealing data are considered in terms of a model in which the formation of antimony-vacancy and antimony-divacancy complexes occur as parallel processes to vacancy capture by sinks. A new energy level at 0.09 eV below the conduction band was observed after annealing at 370°K. The level has been tentatively attributed to oxygen-vacancy complexes.