First-Principles Investigation of Structural and Electronic Properties of the BxGa1-xN, BxAl1-xN, AlxGa1-xN and BxAlyGa1-x-yN Compounds

The structural and electronic properties of the BxGa1-xN, BxAl1-xN, AlxGa1-xN and BxAlyGa1-x-yN 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 AlxGa1-xN, exhibit a downward bowing for both BxAl1-xN and BxGa1-xN, and has a very small deviation when Al is added and a large deviation when B is incorporated for BxAlyGa1-x-yN.The calculated band gap variation for the ternaries shows that the BxGa1-xN has a phase transition from direct-gap to indirect-gap for high boron contents (x > 0.75).As for BxAl1-xN, a direct-gap is found in the boron content range 0.07 < x < 0.83.For AlxGa1-xN and BxAlyGa1-x-yN compounds, they have been found to be direct-gap materials.The results show that the BxGa1-xN, BxAl1-xN, AlxGa1-xN and BxAlyGa1-x-yN materials may well be useful for optoelectronic applications.