Role of Ga flux in dislocation reduction in GaN films grown on SiC(0001)

GaN films are grown by plasma-assisted molecular beam epitaxy on SiC substrates. The width of the x-ray rocking curve for the (1 0 -1 2) reflection exhibits a distinct minimum for Ga/N flux ratios which are only slightly greater than unity. Correlated with this minimum the surface morphology is somewhat rough, with a hill and valley topography. Based on transmission electron micrographs, the reduction in rocking curve width is attributed to enhanced annihilation of edge dislocations due to their tendency to cluster at topographic valleys.