Transmission electron microscopy was carried out to in order to characterize the extended defect reduction in low-defect non-planar GaN substrate templates grown by lateral epitaxial overgrowth. The lateral epitaxial overgrowth non-planar GaN substrate template had a trapezoidal cross-section with smooth (00▪1) and {11▪2} facets. The dislocation distribution and behavior in both ordinary lateral epitaxial overgrowth and 2-step lateral epitaxial overgrowth material were demonstrated here. Penetration of threading dislocations beyond mask windows was observed in ordinary lateral epitaxial overgrowth substrates. In 2-step lateral epitaxial overgrowth substrates, which exploited the tendency of threading dislocations to bend through 90° at certain plane interfaces, only a-type dislocations with a Burgers vector of 1/3<11▪0> were generated in the upper part above the threading dislocation bending zone between 2 mask windows; with a density of about 8 x 107/cm2. There were almost no dislocations in the lateral epitaxial overgrowth wing region. This offered a promising path for producing low-defect GaN substrate templates.

Transmission Electron Microscopy Study of Defect Reduction in Two-Step Lateral Epitaxial Overgrown Nonplanar GaN Substrate Templates. W.Zhou, D.Ren, P.D.Dapkus: Journal of Crystal Growth, 2006, 290[1], 11-7