Micro-Raman spectra of cubic GaN films deposited by MBE on cubic SiC were studied versus the thickness of the underlying SIC film and the deposition rate of the cubic GaN. The residual hexagonal content is found to vary from 0.085 to 3%. The quality of cubic GaN assessed by Raman decreased as the roughness of the (3C) SiC template increased, and the wave number of the TO mode of the cubic phase increased between two plateau values of 553 and 560 cm(-1) as the hexagonal content rose from 0.7 to 1.6%. On the basis of these results, we propose that the cubic GaN is stress-free below 0.7% of hexagonal content, and under an increasing compressive stress as the parasitic phase concentration increases.