The Thermodynamic Stability of In_xGa_{1 – x}N Solid Solutions

Abstract

A theoretical group analysis of the In_xGa_1 – xN solid solutions of indium and gallium nitrides is performed, and all the main symmetry groups with the initial hexagonal structure are found for these solutions. The thermodynamic potentials of the main phases of compositions with different x are calculated by the density functional theory (DFT) method. It is shown that there are a large number of the Pm and P2₁ monoclinic phases that are stable with respect to decomposition into InN and GaN at room temperature in the cases of small and large x, i.e., at 0 < x < 0.2 and 0.8 < x < 1. In the range 0.2 < x < 0.8, there are only two stable Cmc2₁ orthorhombic phases of the compositions with x = 1/3 and 2/3. All the basic geometric and thermodynamic properties of the various phases of In_xGa_1 – xN are calculated. It is found that the stability of epitaxial films of In_xGa_1 – xN increases with an increase in the content of InN and a decrease in the content of GaN.