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

Thermal History Index as a bulk quality indicator for Czochralski solar wafers

“…The diffusion length was above 1 mm at the cell periphery but plummeted below 400 mm at the cell center, leading to the observed η reduction. Such features were previously related to strained oxide precipitates [22,23] We would like to point out here that Si vacancies may play an important role in the oxygen precipitation patterns observed in this study [24]. The correlation between [O i ], THI and bulk-related η losses may thus not be systematic.…”

“…The involvement of oxide precipitates could be ruled out since a thermal donor anneal (10 min at 750°C) performed on asreceived textured and cleaned wafers restored a high carrier lifetime across the wafer [23]. This was indeed not expected if strained oxide precipitates were limiting the lifetime, as such anneal at intermediate T should not induce their dissolution.…”

“…The lifetime-limiting defects in the seed-end region of ingot 1 are thought to be as-grown TD and possibly vacancy-related defects, as demonstrated on seed-end wafers from a twin ingot in [23]. The involvement of oxide precipitates could be ruled out since a thermal donor anneal (10 min at 750°C) performed on asreceived textured and cleaned wafers restored a high carrier lifetime across the wafer [23].…”