The selective lateral growth of GaN with an extremely low dislocation density was achieved, for the first time, directly onto a masked sapphire substrate (without a GaN epitaxial underlayer) via metalorganic vapor phase epitaxy. The mask material and the growth conditions were optimized for this completely selective growth. Dislocation densities of less than 5 x 106/cm2 were obtained when SiN was used as a mask and GaN was used as a low-temperature buffer layer. This reduction in threading dislocation density resulted from a bending of the threading dislocations toward the facet surfaces; as confirmed by cross-sectional transmission electron microscopy. This growth technique was thought to be very promising because a complete device structure with an extremely low dislocation density could be grown by using a single growth process.

Novel Growth Technique for Reducing Dislocation Density in GaN on Sapphire Substrate. T.Kunisato, Y.Nomura, H.Ohbo, T.Kano, N.Hayashi, M.Hata, T.Yamaguchi, M.Shono, M.Sawada, A.Ibaraki: Physica Status Solidi C, 2003, 0[7], 2063-6