Defect reduction in semipolar (11-22) GaN grown on m-sapphire using epitaxial lateral overgrowth

We investigated the optical and the crystal qualities of epitaxial lateral overgrown (ELO) semipolar (11-22) GaN produced using three growth steps: growth of the seed layer for the [11-20] a-direction, the formation of a semipolar (11-22) plane, and the lateral coalescence step with a [11-22] direction. Fully-coalesced ELO-GaN had a good surface morphology and a very low defect density of ∼5.5 10⁵ cm^-2, which was smaller than that of conventional c-plane ELO-GaN. In spite of the generation of some crystallographic tilts, the crystal properties were significantly enhanced as a result of the ELO process. The cathodeluminescence intensity of band edge emission in the low defect region was about 3.1 times higher than in the highly defective region, indicating that the optical properties of semipolar GaN could be significantly enhanced by reducing defects.