Theoretical Investigations of Thermodynamic Stability of III-III-N Semiconductor Alloys

Excess energies and lattice parameters of III-III-N semiconductor alloys, including AlN, GaN and InN, are calculated using a pseudopotential perturbation approach in order to investigate thermodynamic stability. Calculated excess energies of In0.5Ga0.5N, In0.5Al0.5N and Al0.5Ga0.5N with hypothetical chalcopyrite structures have positive values. This result implies that these solid solutions are thermodynamically unstable at 0 K. Validity of Stringfellow's DLP model for semiconductor alloys including them is ascertained based on the calculated excess energies and equilibrium lattice parameters. Using these excess energies, the miscibility gap at high temperatures is discussed by considering free energies.