Investigation on microstructure in GaN epitaxial growth on the stripe-patterned r-plane sapphire substrates

This study reports on the reduction of dislocations in the GaN grown on the stripe-patterned r-plane sapphire substrates via metal-organic chemical vapor deposition (MOCVD). The stripes oriented along the sapphire [1 1 2¯ 0] direction with asymmetrical side faces were fabricated by lithographic and wet-etching processes. The two etching sides of sapphire-striped mesa are {0 0 0 1} and {1 1¯ 0 1} faces. GaN grown on both etching facets exhibits different epitaxial relationships with the sapphire substrate. The GaN grown from the {0 0 0 1} side face of the sapphire mesa contains a low-dislocation density in the order of 107 cm−2. The interfacial regions between the GaN and patterned sapphire substrate are also studied to clarify the behavior of GaN epitaxial growth on the inclined sapphire faces and defect-reduction mechanism.