This paper reviews the impact of doping silicon with substitutional tin impurities on the formation of intrinsic and extrinsic lattice defects. The two major topics covered are ͑i͒ the effect on the diffusivity and aggregation/precipitation of interstitial oxygen in Czochralski ͑CZ͒ silicon and ͑ii͒ the formation of stable radiation defects in irradiated Sn-doped material. As demonstrated, the compressive stress associated with incorporating a large Sn atom on a lattice site is the basic feature governing the interactions with point defects. Consequently, Sn acts as a selective vacancy trap, while, in contrast, not affecting interstitial reactions. This leads to a reduced formation of oxygen thermal donors in n-type Si and lowers the concentration of vacancy-oxygen and divacancy centers in irradiated material. Enhanced oxygen precipitation has been noted around 750°C in p-type CZ silicon. Furthermore, specific Sn-related radiation defects are introduced, which question the use of doping with tin as a technique for substrate hardening.

The beneficial influence of Sn doping of Si materials on the radiation hardness has triggered interest in this material. It is therefore essential to have a good insight in the impact of Sn on the fundamental defect behavior. This report gives a systematic study of the effect of the Sn impurities on the generation and annealing kinetics of oxygen-containing thermal donors formed during a 450ЊC anneal step. Special attention is given to the influence of a thermal preheat treatment at 800ЊC and the important role played by oxygen microfluctuations. The latter act as precursors for the thermal donor formation. The original Kaiser-Frisch-Reiss model, developed for explaining the experimental results in Sn-free Czochralski Si and based on hetero-and homogeneous precipitation processes, points to the beneficial role of Sn doping on the thermal donor properties.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.15.241.167 Downloaded on 2015-03-08 to IP

Different group IV impurities (Pb, C, and Sn) have been introduced in the melt during the growth of n-type Czochralski silicon. The samples have been irradiated with 1 MeV electrons to a fluence of 4x1015cm-2. The irradiation-induced defects have been studied by Deep Level Transient Spectroscopy (DLTS). It is shown that the formation of one of the irradiation-induced deep level is avoided by the Pb-doping. This level is located at 0.37 eV from the conduction band edge (EC) and shows an apparent capture cross-section of 7x10-15cm2. In addition, another irradiation induced deep level located at EC - 0.32 eV has been studied in more details.

Influence of isochronal annealing in the range of 350-1100 • C on the structural properties and the intrinsic absorption edge in thin silicon films doped with tin (a-SiSn) has been studied. It is found that as-deposited a-SiSn films with a tin content of about 4 at.%, unlike undoped a-Si ones, contain silicon nanocrystals with a crystallite size of about 4 nm and a crystalline fraction of about 65%. It is shown that, in the course of isochronal annealing of a-SiSn specimens in the interval of 350-1100 • C, the size of silicon nanocrystals in the amorphous matrix gradually increases to about 7 nm, and the fraction of crystalline phase to about 100%. Crystallization in undoped a-Si is observed only after the annealing at temperatures above 700 • C. The influence of tin on the optical band gap in a-Si as a function of the isochronal annealing temperature is analyzed.K e y w o r d s: thin-film silicon, doping with tin, crystallization, optical band gap, isochronal annealing.