Computational study of adsorption, diffusion, and dissociation of precursor species on the GaN (0001) surface during GaN MOCVD

The adsorption, diffusion, and dissociation of precursor species, MMGa (monomethylgallium) and NH3, on the GaN (0001) surface have been investigated using the DFT (density functional theory) calculation combined with a GaN (0001) surface cluster model. The energetics of NH3(ad) dissociation on the surface proposed the dissociation of NH3(ad) via NH2(ad) to NH(ad) was facile with small activation barriers. A combined analysis with surface diffusion of adatoms demonstrated Ga(ad) and NH(ad) become primary reactant species for 2D film growth, and N(ad) develops into a nucleation center. Our studies suggest the control of NH3(ad) dissociation are essential to improve epitaxial film quality as well as Ga-rich condition. In addition, the adsorbability of H(ad)s resulted from NH3(ad) dissociation were found to influence on the surface chemistry during film growth. (C) 2009 Elsevier B.V. All rights reserved.