An ab initio study of the structural and optoelectronic properties of Al_xGa_(1-x)N (x=0,0.125,0.375,0.625,0.875, and 1) semiconductors

摘要

The structural and optoelectronic properties of AlxGa1-xN (x = 0, 0.125, 0.375, 0.625, 0.875, and 1) semiconductors are studied in detail by applying the full-potential linearized augmented plane-wave method in density functional theory in WIEN2k software. The lattice parameter, the bulk modulus, and its pressure derivative are calculated using the Perdew-Burke-Ernzerhof generalized gradient approximation and by fitting the calculated total energy to the Murnaghan equation. These parameters are found to be in excellent agreement with experimental and theoretical results for both the GaN and AlN compounds. For the Al0.125Ga0.875N, Al0.375Ga0.625N, Al0.625Ga0.375N, and Al0.875Ga0.125N alloys, because of the lack of the theoretical and experimental data, our results can be considered as first predictions. The Tran-Blaha modified Becke-Johnson approach (TB-mBJ) is applied to determine the optoelectronic properties. The results demonstrate that GaN and the AlxGa1-xN alloys with x = 0.125, 0.375, 0.625, and 0.875 have a direct Gamma-Gamma bandgap, whereas the binary AlN compound has an indirect Gamma-X bandgap. Furthermore, the optical properties, such as the dielectric function, refractive index, reflectivity, absorption coefficient, and energy loss function, are presented and discussed in detail; their wide bandgap means that these compounds can be applied in optoelectronic devices for application in the main parts of the ultraviolet and visible spectrum.