Growth of GaN by rf-plasma molecular beam leads to different surface morphologies for nitrogen-rich growth versus gallium-rich growth. Nitrogen-rich growth produces a significant density of pyramidal hillocks while gallium-rich growth results in flat surfaces. Differences in surface morphology were directly linked to the presence of inversion domains which originated in the nucleation layer. Nitrogen-rich growth and growth under atomic hydrogen enhanced the growth rate of inversion domains with respect to the surrounding matrix, while growth under Ga-rich conditions resulted in a more nearly equal growth rate. ©1997 American Institute of Physics.