Published online by Cambridge University Press: 25 February 2003
GaN films were grown using metal-organic chemical vapor deposition (MOCVD) on
intentionally roughened c-sapphire in order to study the effect of the substrate
roughness. Controlled substrate damage was achieved by exposing the substrate
surfaces to controlled amounts of trimethylgallium followed by exposure to hydrogen at
elevated temperature. The bulk film quality was studied by high-resolution X-ray
diffraction and the surface topography was examined by atomic force microscopy. It was
observed that mild substrate roughness (surface pit depth up to 30 nm) does not have a
significant effect on the bulk film quality nor the GaN surface topography, and that
recovery of the surface roughness is observed in very early stages of film growth. Cross
sectional transmission electron microscopy confirmed that MOCVD GaN grown on
inclined sidewalls etched in c-sapphire maintained the $\{0001\}_{\rm sapphire}\parallel\{0001\}_{\rm GaN}$ epitaxial relationship despite the substrate miscut of ca. 15° with respect to the c-axis.