Identification of Lifetime-limiting Defects in As-received and Heat Treated Seed-end Czochralski Wafers

Abstract Major impurity-induced defects in Czochralski silicon are known to be related to oxygen and metallic elements. In this study we focus on seed-end wafers, and submit them to different solar cell process-related annealings. We find that in the as-received state, these seed-end wafers contain a central low carrier lifetime core. We demonstrate that the effective carrier lifetime in the as-received state is simultaneously governed by several defects including oxygen-related thermal donors and a defect deactivated at low temperature. After high temperature steps, a strong recombination center is formed in the central core. Preliminary results of effective carrier lifetime versus temperature measurements directly support oxygen precipitates to be limiting the carrier lifetime. In the light of all results, we propose a qualitative model for the high temperature behavior of these seed-end wafers.