Using various nitrogen active species with different chemical and physical activities, nitridation of Si(111) was studied for the growth of group III nitrides and their alloys using a radio frequency molecular beam epitaxy. Nitrogen inductive coupling discharge produced dissociated active nitrogen atoms (N+N*), which are ground state atom N and excited atom N*, excited molecules N-2*, and molecule ions N-2(+). The surface morphology of beta-SO4 Was affected by the kind of nitrogen species. Flat surface was obtained by using only (N+N*) with slow nitridation of 0.02 ML/s. When nitridation was performed by (N+N*) and N-2*, many steps and many 10 nm height spikes were observed. It was essential for nitridation to eliminate nitrogen ions (N-2(+)). In comparison with this result, when N2* were used, the island size of beta-Si3N4 became bigger without detachment from upper terrace. This island size affected successive surface structure of AlN. It is a key technique to achieve flat surface of beta-Si3N4 that N+N* flux was used for nitridation. The growth of 2H-AlN(0001)/beta-Si3N4/Si(111) structure was also performed. RMS value of AlN grown on beta-Si3N4 which was formed by (N+N*) became 0.88 nm. (C) 2009 Elsevier B.V. All rights reserved.