Films of n-GaN directly deposited on n-SiC by hydride vapor phase epitaxy were studied by means of electron beam induced current (EBIC) and microcathodoluminescence (MCL) measurements. These measurements reveal the presence of a regular pattern of dark line defects in EBIC images and bright line defects in MCL images. The defects are associated with misfit dislocations at the GaN/SiC interface. The density of defects network revealed by MCL is very much lower than the density of defects in the EBIC images because in the former case only the portion of dislocations near which the stress has been relieved are detected. Deuterium implantation leads to complete elimination of the contrast due to misfit dislocations, to strong suppression of the bandedge recombination and to enhancement of the yellow luminescence band.