High-quality films with a low dislocation density and low wing tilt of c-axis orientation were obtained by using air-bridged lateral epitaxial growth. The GaN film was grown from the exposed (00•1) top facet of ridged GaN seed structures, using low-pressure metal-organic vapour-phase epitaxy. The ridge-stripe structures of the GaN seed were constructed in the <1¯1•0>GaN direction. At the optimum growth temperature of 950C, only {11•0} and {00•1} facets were obtained. Continuing growth led to fabrication of the air-bridged structure, where coalescence of the wing region occurred. Transmission electron microscopy showed that most of the vertical dislocations along the c-axis were confined to the seed region, while horizontal dislocations were newly generated in the vicinity of the coalescence boundary. The density of vertical dislocations was about 9 x 108/cm2 in the seed region, but below 106/cm2 in other regions. The density of horizontal dislocations was about 106/cm2 in the wing region and 4 x 107/cm2 in the vicinity of the coalescence boundary. The use of X-ray diffraction revealed that the tilt-angle of the c-axis, relative to the underlying seed, was about 0.083° and the full-width at half-maximum of the X-ray diffraction curve for the wing region was 138arcsec; thus indicating that the wing region had a high uniformity of c-axis orientation.

High-Quality GaN Films Obtained by Air-Bridged Lateral Epitaxial Growth. A.Ishibashi, I.Kidoguchi, G.Sugahara, Y.Ban: Journal of Crystal Growth, 2000, 221, 338-44