First-Principles Investigation of Structural and Electronic Properties of the B x

Abstract

The structural and electronic properties of the $B_{x}Ga_{1-x}N, B_{x}Al_{1-x}N,$ $Al_{x}Ga_{1-x}N$ and $B_{x}Al_{y}Ga_{1-x-y}N$ compounds were studied using the full-potential linearized augmented plane wave method, within the generalized gradient approximation. We have compared the Al and B compositions dependence on the ground state properties: lattice parameters, bulk moduli and their pressure derivative, and band gap energies. The lattice parameters are found to change linearly for $Al_{x}Ga_{1-x}N,$ exhibit a downward bowing for both $B_{x}Al_{1-x}N$ and $B_{x}Ga_{1-x}N,$ and has a very small deviation when Al is added and a large deviation when B is incorporated for $B_{x}Al_{y}Ga_{1-x-y}N$. The calculated band gap variation for the ternaries shows that the $B_{x}Ga_{1-x}N$ has a phase transition from direct-gap to indirect-gap for high boron contents (x > 0.75). As for $B_{x}Al_{1-x}N$, a direct-gap is found in the boron content range 0.07 < x < 0.83. For $Al_{x}Ga_{1-x}N$ and $B_{x}Al_{y}Ga_{1-x-y}N$ compounds, they have been found to be direct-gap materials. The results show that the $B_{x}Ga_{1-x}N,$ $B_{x}Al_{1-x}N,$ $Al_{x}Ga_{1-x}N$ and $B_{x}Al_{y}Ga_{1-x-y}N$ materials may well be useful for optoelectronic applications