A detailed thermodynamic analysis of the system Al-Ga-In-N-C-H was performed using the Gibbs energy minimization method. The multicomponent gaseous phase, ternary liquid alloy of A(III) elements, solid solution of A(III) nitrides as well as graphite and Al4C3 were included into the calculation. The influence of the initial conditions, namely temperature, pressure and input gas phase composition, on the equilibrium composition of this system was in view. On the basis of the concept of local equilibrium between the growing layer and the gaseous phase in its close vicinity, the calculated results were used to optimize deposition parameters for MOVPE growth of (Al,Ga,In)N epitaxial layers. (C) 2004 Elsevier B.V. All rights reserved.