Impacts of off-angle and off-direction on surface morphology of GaN grown by metalorganic vapor phase epitaxy on (0001) GaN substrate

•The macroscopic morphology changes depending on the off-angle and its direction.•Macrostep and hillock form growth is observed below a certain off angle.•The lowest off-angle at which smooth morphology can be obtained is direction-dependent.•The m-direction provide the lowest off-angle and the step flow growth.•The off-angle and off-directions are important factors for morphologies control.