Adatom diffusion at GaN (0001) and (000(1)over-bar) surfaces

The diffusion of Ga and N adatoms has been studied for the technologically relevant wurtzite (<000(1)over bar>) and (0001) surfaces employing density-functional theory. Our calculations reveal a very different diffusivity for Ga and N adatoms on the equilibrium surfaces: While Ga is very mobile at typical growth temperatures, the diffusion of N is by orders of magnitude slower. These results give a very detailed insight of how and under which growth conditions N adatoms can be stabilized and efficiently incorporated at the surface. We further find that the presence of excess N strongly increases the Ga diffusion barrier and discuss the consequences for the growth of GaN. (C) 1998 American Institute of Physics.