The Influence of γ-Irradiation on the Electrophysical Parameters of Nickel-Doped Silicon Grown by the Czochralski Method

The effect of γ-irradiation on the electrophysical parameters of silicon doped with nickel during growth from melt according to the Czochralski method was studied. Experimental results obtained by scanning electron microscopy showed that clusters of Ni atoms ~6–8 μm in size with a surface density of ~(5–8) × 103 cm–2 were formed in nickel-doped silicon during cultivation. It was established that, during irradiation with γ-quanta 60Co of the control samples not doped with nickel, material compensation occurs due to the generation of deep centers of radiation origin. In silicon samples doped with nickel, when irradiated with γ‑quanta, the size of the clusters decreased, and the concentration of free charge carriers changed slightly: when the fluence increased to F ≥ 3 × 108 rad, and the resistivity decreased by no more than 30%. Such a change in the parameters of Si〈Ni〉 samples is due to the formation of acceptor centers because of an increase in the concentration of electrically active nickel atoms. It was shown that nickel atoms diffuse from clusters into the silicon matrix during irradiation, whereupon interaction with radiation-generated vacancies interstitial nickel atoms Nii pass into electrically active position in the Nis crystal lattice unit. Those impurity defect centers (Nis) were thermally stable to at least an annealing temperature of 600°C.