Phase separation and ordering in group-III nitride alloys

The electronic, structural, and thermodynamic properties of cubic (zinc blende) group-III nitride ternary In xGa1-xN and quaternary Al xIn yGa1-x-yN alloys are investigated by combining first-principles total energy calculations and cluster expansion methods. External biaxial strain on the alloys are taken into account in the calculations. While alloy fluctuations and strain effects play a minor role in the physical properties of AlGaN, due to the small lattice-mismatch, in the InGaN alloys we found a remarkable influence of strain on the phase separation. The effect of biaxial strain on the f...