Effects of gallium as a surfactant for the growth of AlN epilayers on SiC substrates by metal-organic chemical-vapour deposition have been studied. It was found that the use of gallium as a surfactant enables the growth of thick, crack-free AlN epilayers on SiC substrates. The photoluminescence and x-ray diffraction (XRD) analysis show that gallium surfactant can reduce some of the tensile strain in AlN epilayers and it improves the surface smoothness. XRD rocking curves yielded decreased full widths at half maximum for the (1 0 5) and (0 0 2) reflections, indicating a reduction in threading dislocation density in the AlN epilayers.