The effect of the Ga/N flux ratio upon the surface morphology, incorporation of point defects and electrical transport properties of GaN films grown by plasma-assisted molecular beam epitaxy in a recently developed high-temperature growth regime was investigated. The homo-epitaxial (00•1) GaN films, grown at 780 to 790C, exhibited the smoothest morphologies near to the cross-over between N-rich and Ga-rich growth (0.75 < Ga/N < 1.1); contrasting with previous observations for low-temperature growth. The higher-quality growth near to Ga/N ∼ 1 resulted from lower thermal decomposition rates and was associated with slightly lower Ga vacancy concentrations [VGa], lower non-intentional oxygen incorporation and improved electron mobilities. The consistently low [VGa], i.e., ∼1016/cm3 for all films further demonstrated the significant benefits of high-temperature growth.

Influence of Ga/N Ratio on Morphology, Vacancies, and Electrical Transport in GaN Grown by Molecular Beam Epitaxy at High Temperature. G.Koblmüller, F.Reurings, F.Tuomisto, J.S.Speck: Applied Physics Letters, 2010, 97[19], 191915