MOCVD Growth of GaN on bulk AlN Substrates

Abstract

AbstractIn this paper, the growth of epitaxial GaN layers on c-plane and a-plane bulk AIN substrates by metalorganic vapor phase epitaxy is reported. The AlN boules were grown by the sublimationrecondensation technique. Single crystal GaN films grown on the c-plane orientation replicate the substrate orientation. However the surface of the epilayer had a high density of cross-hatch defect lines, presumably caused by mechanical polishing damage. The low temperature PL spectra of these films were dominated by exciton emission at 3.470 eV with a FWHM of 14 meV at 7 K. On the other hand, GaN grown on the a-plane orientation AlN was polycrystalline and the surface was rough with ridge-like facets. The PL from this film showed a dominate peak at 3.406 eV which may originate from defect-bound excitons. The quality of the GaN layers grown on these AIN bulk substrates appeared to be limited by the surface preparation method, which has not been optimized.