Morphological and structural characteristics of homoepitaxial GaN grown bymetalorganic 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 mu m in size de pending on layer thickness). The evolution of the pyramidal defects is domi nated 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 c ontaining amorphous material (2-5 nm in thickness), being remnant contamina tion from the mechano-chemical polishing technique used to prepare the subs trates prior to growth. Apart from pyramidal hillocks, the flat-topped hill ocks art: also formed. The arguments are presented on the association betwe en these features and the core dislocations, which constitute the source of the growth steps. Improvement in the substrate polishing procedures allowe d the effective elimination of these surface hillocks. (C) 1999 Elsevier Sc ience B.V. All rights reserved.