The intensity of the infrared absorption band at 1107 cm(-1) related to interstitial oxygen (Os) concentration, decreased as the Ge concentration increased in Ga and Ge codoped CZ-Si crystals. In contrast, the number of precipitates observed on the etched surfaces of CZ-Si wafers increased as the Ge concentration increased. From an energy dispersive X-ray (EDX) analysis, O was observed to be one of the major components of the precipitates. Moreover, Ge was found as one of the components in the precipitate observed on the heavily Ge (> 1 x 10(18) cm(-3)) codoped CZ-Si wafers. These results suggest that the grown-in O precipitates increase as the Of concentration decreases when the Ge concentration increases in the Si crystal. The Ge-vacancy (V) complex in the Si lattice probably acted as a heterogeneous nucleation center and may enhanced the grown-in O precipitates thereby reducing the dissolved O(i) concentration in the Si lattice. (C) 2011 Elsevier B.V. All rights reserved.