Direct heteroepitaxial lateral overgrowth of GaN on stripe-patterned sapphire substrates with very thin SiO2 masks

Direct heteroeptaxial lateral overgrowth of GaN was performed on sapphire substrates by low-pressure metalorganic chemical vapor deposition. The substrates were patterned with very thin SiO2 stripes with the thickness of 200 similar to 300 Angstrom. The growth was carried out by a two-step condition. In the first step for facet-controlled epitaxy, the formation of a triangular cross-section of GaN stripes grown directly on the patterned sapphire was achieved to terminate threading dislocations (TDs) in the opening regions on the inclined {1-22} facets. During the second step for lateral growth, the TDs were bended completely by strong lateral overgrowth. The densities of the step terminations in atomic force microscopic images, corresponding screw- or mixed-type TDs were effectively reduced to less than 10(7) cm(-2) over the entire region. The crystallographic tilt between the mask and the opening regions was also well suppressed by using the very thin SiO2 mask as thick as GaN nucleation layer.