Growth of GaN on patterned sapphire substrate with high-index facets

Periodic pyramidal array patterned sapphire substrate (PSS) with various inclined facets was fabricated by wet etching. It was found that {34^-17}, {41^-3^-18}, and {123^-5} facets are exposed on the PSS structure after etching. GaN grown on the PSS by metal-organic chemical vapor deposition was found to have a semi-polar orientation by structural characterization with scanning and transmission electron microscopy. Also, the results show that GaN is mainly grown on the {123^-5} sapphire facet with the orientation relationship between GaN and sapphire as (011^-4^-)GaN // (33^-06^-)sapphire and [022^-1]GaN // [112^-0]sapphire, and the dislocation density in the grown GaN decreased with thickness. In addition, photoluminescence and catholuminescence measurements show only strong near-band-edge emission from the semi-polar GaN on the {123^-5} sapphire facet.