How to grow cubic GaN with low hexagonal phase content on (001) SiC by molecular beam epitaxy

Molecular beam epitaxy (MBE) of cubic GaN on SiC films deposited by chemical vapor deposition on Si has been investigated by reflection high-energy electron diffraction, x-ray diffraction, photoluminescence, and micro-Raman spectroscopy. The wurtzite/zinc-blende ratio, indicative of the material quality, has been found to depend on both the initial substrate roughness and the N/metal ratio impinging on the surface. The results were consistently analyzed by assuming that the MBE growth of cubic GaN is mainly governed by the impinging active N flux, which directly determines the mean-free path of Ga adatoms.