Calculation of unstable mixing region in wurtzite In1−x−yGaxAlyN

Abstract

The wurtzite structure In1−x−yGaxAlyN quaternary system with a wide band gap, which is useful for light emitters in the wavelength region shorter than green, is studied with respect to the unstable region in mixing. This unstable region in mixing is calculated from the free energy of mixing using the strictly regular solution model. The interaction parameter used in this calculation is obtained using the delta-lattice-parameter method. From this calculation, the ternary alloys of InAlN, InGaN, and GaAlN are, respectively, predicted to always, sometimes, and hardly ever have a unstable mixing region at the temperature lower than 3000 °C.