Morphological and structural characteristics of homoepitaxial GaN grown by metalorganic chemical vapour deposition (MOCVD)

MOCVD-grown GaN on the N-polar surface of GaN substrates has been found to exhibit gross hexagonal pyramidal features (typically 10}50 lm in size depending on layer thickness). The evolution of the pyramidal defects is dominated by the growth rate of an emergent core of inversion domain (typically 100 nm in size). The inversion domains nucleate at a thin band of oxygen containing amorphous material (2}5 nm in thickness), being remnant contamination from the mechano-chemical polishing technique used to prepare the substrates prior to growth. Apart from pyramidal hillocks, the #at-topped hillocks are also formed. The arguments are presented on the association between these features and the core dislocations, which constitute the source of the growth steps. Improvement in the substrate polishing procedures allowed the e!ective elimination of these surface hillocks. ( 1999 Elsevier Science B.V. All rights reserved.