Surface-catalyzed decomposition of ammonia in MOCVD growth of III-nitrides

The amount of ammonia available at the growth surface during metalorganic chemical vapor deposition of III-nitrides differs significantly from the reactor input. It depends not only on reactor design but also on the properties of the growth surface. To predict the surface chemical potentials and the kinetics governing growth, we developed a quantitative model that incorporates catalytic decomposition reactions at the surface. Our results show that, depending on surface polarity and carrier gas, at least two orders of magnitude more ammonia is lost through decomposition than is incorporated into growth. Decomposition is particularly pronounced for N-polar surfaces when nitrogen is used as the carrier gas. This model enables prediction and control of surface morphology, as well as the incorporation of point defects.