Direct lateral epitaxy overgrowth of GaN on sapphire substrates based on a sparse GaN nucleation technique

A sparse nucleation process on sapphire (0001) substrates has been developed for the growth of GaN thin films. The density of nucleation sites is reduced to only 4 × 10⁴cm^-2. Based on this process, we performed direct lateral epitaxial overgrowth (LEO) of GaN by metalorganic chemical vapor deposition on patterned SiO₂/sapphire (0001) substrates. An aggregate lateral to vertical growth rate ratio of around 2:1 was achieved after the coalescence of the GaN stripes. Cathodoluminescence imaging shows strong and uniform near-band gap luminescence from LEO regions and confirms the improved quality of LEO GaN, which is further supported by atomic force microscopy analysis.