Heavily tin (Sn)-doped Si crystals in a concentration up to 4×10 19 cm-3 were grown by the Czochralski method. Variation of Sn concentration in the crystals was well expressed by the Pfann equation using a segregation coefficient of k=0.016. From the occurrence of growth interface instability and the appearance of Sn precipitates in the grown crystals, the solubility limit of Sn was considered to be around 5×1019 cm-3. Interstitially dissolved oxygen Oi was presented at a concentration of 8-9×1017 cm-3 in the grown Sn-doped crystals. The FT-IR absorption peak relating to a Si-Oi-Si quasi-molecule at 1106 cm-1 showed preferential occupation of O i at the bond-centered position of Si-Si. The Oi peak shifted to the lower wave number side with increasing Sn concentration in Si, implying expansion of the Si-Si bond.
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