Particularities of the formation of radiation defects in silicon with low and high concentrations of oxygen

A comparative study is made on the radiation damage caused by fast-pile neutrons in n-Si with low and high concentrations of oxygen by measuring the effective carrier concentrations and energies of defects. The role of clusters in degrading Si parameters was studied both experimentally and theoretically. It has been shown experimentally that the fluence for which the carrier concentration tends to the intrinsic value does not depend on the oxygen concentration. The theoretical calculation has been carried out in the framework of Gossick's corrected model. The additional overlapping of clusters due to introduce of defects is explained. The model of the n -> p conversion in n-Si with various oxygen concentrations is presented. It is shown that divacancy and di-interstitial congestions are responsible for the Fermi level position near the midgap at high fluences. Analysis of V defect levels gave evidences of increase of level energy in the forbidden band on capture of the first or the second electron on the value Delta E = 0.33/xi, where 1 <= xi <= 5. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim