The behavior of as-grown oxygen precipitation in Czochralski (Cz) silicon (Si) with the germanium (Ge)-doping has been investigated. It is found that the as-grown oxygen precipitation in Ge-doped Cz (GCz) Si can be enhanced in comparison with the conventional Cz Si at high temperatures, even above the formation temperature of void. It has been ascribed to the effect of heterogeneous nucleus sites supplied by the Ge-related complexes generated in GCz Si. Meanwhile, more large-sized as-grown oxygen precipitates can be formed in GCz Si is revealed through both a controlled ramping annealing and an isothermal annealing performed at high temperatures. This phenomenon is considered to be associated with the reduction in the critical radius of oxygen precipitates for the elevated temperatures. (c) 2006 Elsevier B.V. All rights reserved.