Nucleation and growth behavior for GaN grown on (0001) sapphire via multistep growth approach

Formation and coalescence of GaN truncated three dimensional islands (TTIs) on (0001) sapphire are observed during growth of GaN using a close spaced metalorganic chemical vapor deposition reactor. To encourage formation of TTIs to occur uniformly over the buffer layer, growth conditions are chosen under which thermal desorption and/or mass transport of the buffer layer can be suppressed. During coalescence of TTIs, growth conditions that favor higher desorption of species on the GaN (0001) surface and incorporation on other planes are beneficial. Therefore, changing the growth conditions as the growth mode changes is effective to obtain both good crystallinity and flat surface morphology.