Effect of an Al pre-seeded AlN buffer on GaN films grown on Si(111) substrates by using SiC intermediate layers

Low-pressure metalorganic chemical-vapor deposition was used to grow single- crystal hexagonal GaN films with an Al pre-seeded AlN buffer layer on Si(111) substrates by using SiC intermediate layers. The crystal quality and the surface morphology of GaN films were found to strongly depend on the Al pre-seeding time because the Al pre-seeding procedure prevented the formation of SixNy at the 3C-SiC surface. The crystal quality and the surface morphology of the GaN films were improved with increasing Al pre-seeding time. The optimized Al pre-seeding time was 20 s. The full width at half maximum (FWHM) of the PL spectra of an GaN epilayer grown at the optimized Al pre-seeding time was 42.0 meV, and the FWHM of X-ray diffraction rocking curve for the GaN (0002) plane was 649.584 arcsec. The root-mean-square value of the surface roughness of the GaN was 2.11 nm, and the crack density was reduced.