The mechanisms of GaAs1−xNx film growth by plasma-assisted molecular-beam epitaxy were investigated. A comparison of in situ reflection high-energy electron diffraction and scanning tunnelling microscopy, with ex situ atomic force microscopy, revealed a temperature-dependent interplay between surface and step-edge diffusion. At low temperatures, layer-by-layer growth was observed, presumably due to limited adatom surface mobility. As the temperature increased, the interplay between surface and step-edge diffusion leads to multilayer growth. For sufficiently high temperatures, adatoms overcome the step-edge diffusion barrier, resulting in layer-by-layer growth once again. The temperature range for multilayer growth was influenced by the Ga flux and may be narrowed by using As2. Using in situ scanning tunnelling microscopy, the activation energies for Ga surface diffusion, Ed, and step-edge diffusion, Ee, during layer-by-layer GaAsN growth were quantified. Estimates of Ed = 0.75 and 0.96eV were obtained for growth using As4 and As2, respectively. Thus, the narrowing of the multilayer growth temperature range was likely to be  due to the decrease in Ga surface diffusion length through the use of As2 in lieu of As4. Furthermore, it was estimated that Ee = 80meV. This was larger than that reported for GaAs growth.

Mechanisms of GaAsN Growth - Surface and Step-Edge Diffusion. M.Reason, N.G.Rudawski, H.A.McKay, X.Weng, W.Ye, R.S.Goldman: Journal of Applied Physics, 2007, 101[8], 083520