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

Abstract

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 ξ 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 ∆E = 0.33/ξ, where 1 ≤ ξ ≤ 5.

Dependence of the defect introduction rate on the dose of irradiation of p-Si by fast-pile neutrons

“…In [8], the original scheme of energy levels for intrinsic radiation defects, which is based both on the literature data and the original experiment, was proposed. It takes the following positions into account: (i) radiation defects form the additional energy levels in the forbidden band, and the intrinsic defects in silicon are amphoteric; (ii) under capture of one or two electrons on acceptor levels of a divacancy or a di-interstitial, the position of levels in the forbidden gap of silicon is changed by the value ∆Е 0 = 0.165 ± 0.005 eV, and, in the case of vacancies or interstitials, the mentioned value is added twice; (iii) the modification of a divacancy by carbon increases the energy position of acceptor levels by the value ∆Е 1 = 0.035 eV and decreases the energy of donor levels, whereas the addition of oxygen to a divacancy decreases the acceptor level energy and increases the donor level energy of a divacancy by the value ∆Е 2 = 0.06 eV.…”

“…The analysis and the results presented in [8] gave us a possibility to determined the fact that the energy of acceptor levels is increased by value ∆Е = 0.33 / ξ under the electron capture, where ξ is the number of vacancies in the multivacancy defects (1 ≤ ξ ≤ 5).…”

“…We assume (see the Table in [8]) that Е v + 0.42 eV belongs to the acceptor level of interstitial levels (I −/0 ), and Е v + 0.45 eV belongs to the donor level of diinterstitials (I 2 0/+ ). The increase in the number of negatively polarized oxygen neighbors in the series of C i , C i O i , C i O 2i leads to an upward shift of their donor levels:…”

“…The process of accumulation of the clusters of defects in a separate volume is similar to the activation and decay of radioactive nuclei. Thus, the volume fraction (f ), occupied by clusters (due to the introduction of point defects), with regard for the overlapping of clusters in accordance with [3], can be evaluated as…”

Radiation-Stimulated Changes in the Characteristics of Surface-Barrier Al–Si–Bi Structures with Different Concentrations of Dislocations at the Crystal Surface

“…In the recent years there have appeared a significant number of publications devoted to the regularities of changes occurring to the parameters and characteristics of surface-barrier structures (SBSs) made of silicon, as well as to diode structures subjected to the magnetic and irradiation fields (Borkovska et al, 1984;Mahkamov et al, 1999;Nikolaev et al, 2003;Marchenko et al, 2010;Kalinina et al, 2010;Dolgolenko et al, 2006;Makara et al, 2008;Skvortsov et al, 2009;Mudriy et al, 2010). It is now well established (Borkovska et al, 1984;Mahkamov et al, 1999;Nikolaev et al, 2003;Marchenko et al, 2010;Kalinina et al, 2010;Dolgolenko et al, 2006) that the irradiation stimulates evolution of defect structure of crystals and so can lead to either deterioration or improvement of many characteristics of the silicon structures. Though being somewhat unusual, the latter effect really exists and is known as an 'effect of small doses'.…”