We determined the polarities of { 0 0 0 1} GaN films and { 111} 3C-SiC intermediate layers grown on 3 in I I I I Si substrates by metalorganic vapor phase epitaxy (MOVPE). The polarities were determined by convergent beam electron diffraction (CBED) using transmission electron microscopy. The polarities of the GaN films and the 3C-SiC intermediate layers were determined as Ga and Si polarities, respectively. The etching of the GaN films using an aqueous KOH solution resulted in a smooth surface, thereby indicating Ga polarity; this supports the results obtained by CBED. The model of the interfacial structure was proposed. We concluded that the GaN films on Si substrates using 3C-SiC intermediate layers are promising for the fabrication of nitride-based electronic devices. (c) 2006 Elsevier B.V. All rights reserved.