Enhanced two-dimensional growth of MOVPE InN films on sapphire (0001) substrates

Abstract MOVPE growth of InN on sapphire substrates is compared using two different designs of horizontal reactor. The major difference between the two designs is a variation in the reactant-gas flow-spacing between the substrate and the ceiling of the quartz chamber: 33 mm for the Type A reactor and 14 mm for Type B. Compared with the Type A reactor, the Type B reactor brings about InN films with a larger grain size. This is especially true when InN is grown at 600°C using the Type B reactor, in which case the two-dimensional (2D) growth of InN is found to be extremely enhanced. An investigation of the NH 3 /TMIn molar ratio dependence of the surface morphology of grown InN films using the two reactors suggests that the enhanced 2D growth is attributed to the decrease in the effective NH 3 /TMIn ratio in the growth atmosphere. Even using the Type A reactor, a film with enhanced 2D growth can be obtained when the NH 3 /TMIn ratio is considerably low (∼1.8×10 4 ). The enhanced 2D growth results in a smaller XRC-FWHM (full-width at half maximum of the X-ray rocking curve) (⩽1500 arcsec), than that for a 3D-grown film (∼5000 arcsec).