The effect of germanium (Ge) on void defects in lightly Ge-doped Czochralski (GCZ) silicon (Si) crystals has been investigated. Three GCZ Si crystals with different Ge concentrations (10(15)-10(18) cm(-3)) and one conventional Czochralski (CZ) Si crystal were grown under almost the same growth conditions. It is found that the density of flow pattern defects (FPDs) related to void defects in the as-grown GCZ Si decreases with the increase of Ge concentration. The voids in the GCZ Si could be eliminated more easily during annealing at the high temperatures of 1050-1200degreesC. It is concluded that Ge can suppress the formation of voids during Si crystal growth. Thus, GCZ Si can be expected to use widely in modern microelectronic industry. (C) 2002 Elsevier Science B.V. All rights reserved.