GaN has been intensively studied because of its potential applications for the fabrication of blue- or ultraviolet-light emitting devices. Sapphire (α-Al2O3) is generally used as the substrate for growth of GaN film. However, the large lattice mismatch between GaN and Al2O3is a possible cause of the large defect density in the GaN films. Consequently, alternative substrates are being studied with the aim of growing films of lesser defect densities and improved opto-electronic properties. In this paper, we report a transmission electron microscopy (TEM) study of a GaN film grown on cubic SiC which has been obtained by carbonization of the top silicon layer of a SIMOX substrate, i.e. the system GaN/SiC/Si/SiO2/Si.

Cross-sectional TEM specimens were prepared by the conventional sandwich technique with the foil surface normal to the Si[l10] direction. The composite sample was ground and dimpled to a thickness of ∼ 10μm, and subsequently ion thinned to electron transparency.