Crystal structure of GaN grown on 3C-SiC substrates by metalorganic vapor phase epitaxy

GaN films were grown on 3C-SiC substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the N source. The crystal structure was strongly affected by both the growth temperature and the V/III ratio. At 600 degrees C, only hexagonal GaN films with their c-axis perpendicular to the substrate surface were grown. At 800 degrees C, relatively high V/III ratios resulted in the growth of hexagonal GaN with their c-axis oriented in the [111] direction while cubic GaN films were obtained at lower V/III ratios. The origin of [111]-oriented hexagonal GaN is also discussed.