GaN hexagonal microprisms with smooth vertical facets fabricated by selective metalorganic vapor phase epitaxy

Selective growth of GaN was performed by low-pressure metalorganic vapor phase epitaxy using a mask-patterned GaN epitaxial layer on a (0001) sapphire substrate. GaN hexagonal microprisms of 5–16 μm in diameter, with smooth vertical facets and no ridge growth, were fabricated on a (0001) sapphire substrate. This vertical {11̄00} facet of GaN was parallel to a {112̄0} face of the sapphire substrate. Both the use of an epitaxial GaN layer on the sapphire substrate and low working pressure contributed to obtaining smooth top and vertical facet surfaces. Also, the stripe structures of GaN were obtained that had a rectangular cross section. Moreover, the selection of the mask-patterning direction was found to be important because of the 30° rotation of the crystallographic orientation between the GaN layer and the sapphire substrate.