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Microstructure and thermal stability of the radiation defects in n-FZ-Si ([P] ≈ 7 × 10(15) cm(-3)) single crystals have been investigated. The radiation defects have been induced by irradiation with 15 MeV protons and studied by means of both the positron lifetime spectroscopy and low-temperature measurements of the Hall effect. At each step of the isochronal annealing over the temperature range ∼60-700 °C the positron lifetime has been measured for the temperature interval ∼30-300 K, and for samples-satellites the temperature dependences of the charge carriers and mobility have been determined over the range ∼4.2-300 K. It is argued that as-grown impurity centers influence the average positron lifetime by forming shallow (E(b) ≈ 0.013 eV) positron states. The radiation-induced defects were also found to trap positrons into weakly bound (E(b) ≤ 0.01 eV) states. These positron states are observed at cryogenic temperatures during the isochronal annealing up to T(anneal.) = 340 °C. The stages of annealing in the temperature intervals ∼60-180 °C and ∼180-260 °C reflect the disappearance of E-centers and divacancies, respectively. Besides these defects the positrons were found to be localized at deep donor centers hidden in the process of annealing up to the temperature T(anneal.) ≈ 300 °C. The annealing of the deep donors occurs over the temperature range ∼300-650 °C. At these centers positrons are estimated to be bound with energies E(b) ≈ 0.096 and 0.021 eV within the temperature intervals ∼200-270 K and ∼166-66 K, respectively. The positron trapping coefficient from these defects increases from ∼1.1 × 10(16) to ∼6.5 × 10(17) s(-1) over the temperature range ∼266-66 K, thus substantiating a cascade phonon-assisted positron trapping mechanism whose efficiency is described by ≈T(-3) law. It is argued that the value of activation energy of the isochronal annealing E(a) ≈ 0.74-0.59 eV is due to dissociation of the positron traps, which is accompanied by restoration of the electrical activity of the phosphorus atoms. The data suggest that the deep donors involve a phosphorus atom and at least two vacancies. Their energy levels are at least at E > E(c) - 0.24 eV in the investigated material.

The formation kinetics of Thermal Double Donors, a dominant family of thermal donors in Czochralskigrown silicon annealed at T < 600 °C, is studied in detail. A striking enhancement effect of hydrostatic pressures of about 1 GPa on their formation processes, even in a temperature region of thermal instability of these donor centers at about T = 600 °C under normal conditions, is clearly demonstrated. The experimental data obtained in the present work are in agreement with the recent theoretical calculations of oxygen diffusion and agglomeration processes in heat-treated Si.It is well known that oxygen impurity atoms in Czochralski-grown silicon (Cz-Si) being available in concentrations much higher than the oxygen solubility at room temperature are prone to agglomeration upon heating. Heat treatment of Cz-Si at T < 500 °C gives rise to the formation of a family of Thermal Double Donors (TDDs) consisting of more than 16 centres with shallow and deep energy states in the regions between 44 meV and 70 meV and between 100 meV and 150 meV, respectively [1, 2]. The electrical properties of Cz-Si heat treated at T < 500 °C are mainly determined by this family of thermal donors. The characteristic features of oxygen diffusion and agglomeration processes in annealed Cz-Si have recently been reviewed in [3]. Despite a vast amount of information available in the literature the key steps in these processes are still a matter of discussion. Among many well-known factors producing considerable effects on the TDD formation processes, e.g. heat-treatment regimes, the presence of isovalent impurities C and Ge, and so on, the effects of compressive stresses of about 1 GPa leading to enhanced formation of thermal donors in annealed Cz-Si [4,5] are relatively little studied. The purpose of the present work is to study the formation kinetics of TDDs in a more systematic way. This provides a solid basis for computational simulations giving a clue for the complex nature of oxygen aggregates in Si.

Effects of irradiation with 0.9 MeV electrons as well as 8 and 15 MeV protons on moderately doped n Si grown by the floating zone (FZ) technique and n SiC (4H) grown by chemical vapor deposition are studied in a comparative way. It has been established that the dominant radiation produced defects with involvement of V group impurities differ dramatically in electron and proton irradiated n Si (FZ), in spite of the opinion on their similarity widespread in literature. This dissimilarity in defect structures is attributed to a marked difference in distributions of primary radiation defects for the both kinds of irradiation. In con trast, DLTS spectra taken on electron and proton irradiated n SiC (4H) appear to be similar. However, there are very much pronounced differences in the formation rates of radiation produced defects. Despite a larger production rate of Frenkel pairs in SiC as compared to that in Si, the removal rates of charge carriers in n SiC (4H) were found to be considerably smaller than those in n Si (FZ) for the both electron and proton irradiation. Comparison between defect production rates in the both materials under electron and proton irradiation is drawn.

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