Phase separation and ordering in group-III nitride alloys

Abstract

The electronic, structural, and thermodynamic properties of cubic (zinc blende) group-III nitride ternary InxGa1−xN and quaternary AlxInyGa1−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 formation of ordered phases has been also investigated, and the results are used to clarify the origin of the light emission process in InxGa1−xN based optoelectronic devices. The dependence of the lattice constant and energy bandgap in quaternary AlxInyGa1−x−yN alloys was obtained as function of the compositions x and y.

Surface and in-depth characterization of InGaN compounds synthesized by plasma-assisted molecular beam epitaxy

“…One of the widely discussed features of InGaN compounds is the compositional inhomogeneity, which is usually considered as a compositional fluctuation or phase separation in the alloy growth [5][6][7][8]. Based on X-ray diffraction (XRD) and optical absorption studies, Singh and co-workers [5] provided a strong evidence of phase separation in InGaN thick films grown by molecular beam epitaxy (MBE).…”

Band gap bowings and anomalous pressure effects in III–V nitride alloys: Role of In‐segregation

“…It should be added that we have here only considered some structural effects on materials with fixed atoms. Inclusion of thermal effects and strain will further complicate the investigations 14, 15.…”

Optical band gap energy values in wurtzite InxGa1-xN

“…Previous studies of In x Ga 1-x N compounds showed poor agreement of the DFT band gap values with experimental data [12,22,[40][41][42][43][44]. To improve consistency between theory and experiment, hybrid functionals in DFT have been used as an empirical simulation method.…”