We investigated the growth conditions of cubic GaN (c-GaN) by ab initio-based approach which incorporates free energy of vapor phase. It is known that a c-GaN is a metastable phase and wurtzite GaN (h-GaN), which is a stable phase of GaN, is easily incorporated in the c-GaN crystal during growth. h-GaN is formed in the area grown on {111} faceted surface. In the present study, therefore, we studied the growth conditions of {111} facet formation in order to suppress h-GaN mixing. The results suggest that we can suppress the {111} facet formation, i.e., h-GaN mixing, by controlling the growth conditions such as temperature and gallium beam equivalent pressure. (C) 2009 Elsevier B.V. All rights reserved.