  We report the growth of high-quality triangular GaN nanomesas, 30-nm thick,
on the C-face of 4H-SiC using nano selective area growth (NSAG) with patterned
epitaxial graphene grown on SiC as an embedded mask. NSAG alleviates the
problems of defective crystals in the heteroepitaxial growth of nitrides, and
the high mobility graphene film can readily provide the back low-dissipative
electrode in GaN-based optoelectronic devices. The process consists in first
growing a 5-8 graphene layers film on the C-face of 4H- SiC by
confinement-controlled sublimation of silicon carbide. The graphene film is
then patterned and arrays of 75-nanometer-wide openings are etched in graphene
revealing the SiC substrate. 30-nanometer-thick GaN is subsequently grown by
metal organic vapor phase epitaxy. GaN nanomesas grow epitaxially with perfect
selectivity on SiC, in openings patterned through graphene, with no nucleation
on graphene. The up-or-down orientation of the mesas on SiC, their triangular
faceting, and cross-sectional scanning transmission electron microscopy show
that they are biphasic. The core is a zinc blende monocrystal surrounded with
single-crystal hexagonal wurtzite. The GaN crystalline nanomesas have no
threading dislocations, and do not show any V-pit. This NSAG process
potentially leads to integration of high-quality III-nitrides on the wafer
scalable epitaxial graphene / silicon carbide platform.
