Low-dislocation-density, nonplanar GaN templates for buried heterostructure lasers grown by lateral epitaxial overgrowth

We report here the formation of nonplanar GaN templates, which consist of low-dislocation-density, naturally grown GaN ridge mesas, as a mean to facilitate the fabrication of buried heterostructure lasers. Defect reduction is realized by introducing a two-step lateral epitaxial overgrowth procedure that utilizes dislocation bending in the formation of pyramidal mesas to eradicate the threading dislocations that originate from a planar buffer layer. Transmission electron microscopy and atomic force microscopy indicate a mesa top facet having low defect density (∼8×10⁷ cm^-2), atomic flatness (∼0.29 nm mean roughness). Our demonstration has opened the possibility of forming buried heterostructure lasers on nonplanar GaN templates.