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 {317}, {418}, and {125} 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 {125} sapphire facet with the orientation relationship between GaN and sapphire as (01)GaN// (30)sapphire and [021]GaN // [110]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 {125} sapphire facet.