New approach for calculation of the GaxAl1−xN solid-state alloys

A novel method for calculating the band structure of the GaxAl1−xN solid-state alloys (with x=0.15; 0.52 and 0.65) was proposed. This approach consists in the orthogonalisation procedure for the plane wave basis set with respect to the core-like orbitals and the application of the Perdew–Alder exchange–correlation scheme. Experimental ellipsometric data and X-ray photoelectron spectra were used as a criterion of preferability between the different calculation techniques. The results of traditional one-electron methods of band structure calculations (e.g. self-consistent norm-conserving pseudo-potential (NCPP), linear muffin tin orbital method (LMTO), full linear augmented plane wave (FLAPW) and linear combination atomic orbital (LCAO) methods) are compared with the experimental data. We demonstrate that better agreement with experiment is achieved when the NCPP wavefunctions are orthogonalised to the 3dGa core-like states. Due to using of the mentioned procedure a better agreement with experimental X-ray photoelectron spectroscopy and ellipsometric data is achieved. Concerning the LMTO and the FLAPW all-electron methods, only appropriate application of the virtual crystal approximation to these approaches produces results that are in agreement with the proposed modified NCPP method.