We have studied the change in the Gibbs free energy during the formation of a pseudo-binary compound with InN-GaN nanostructures. The addition of a free energy term regarding the surface energy and the radius of curvature in the nanostructure leads to a modulation of the phase diagram for the corresponding bulk. We considered the actual parameters extracted from the InGaN system and found that the binodal and spinodal curves became closer with decreasing radius of the nanostructure; 1) the solid solubility of InN in GaN was promoted, which enhancement became more prominent at a higher growth temperature, and 2) the metastable region formed between the binodal and the spinodal curves became narrower, but the inhomogeneous region under the spinodal decomposition curves became slightly broader. We also found a critical minimum radius, which is inversely proportional to the growth temperature, for the InGaN nanostructures under equilibrium growth conditions. 

Keywords: InGaN, Phase separation, Miscibility gap, Solid solubility, Nanostructure