Micro-Raman and photoluminescence experiments have been performed to characterize the polycrystalline region in the wafers cut from a bulk In(x)Gal(1-x)As crystal, which was found to be initiating from the inner part of the ingot, unlike the usual observation of polycrystallization starting from the peripheral part of an ingot. This indicates the existence of polycrystallization mechanism other than those relating to the boundary effects. The polycrystalline region was found to have a random fluctuation of composition. The possibility of drastic local fluctuation in composition, which can be occurred by convection-induced local supercooling, being the main cause of polycrystallization, is investigated here. (C) 2003 Elsevier B.V. All rights reserved.