First-principles calculations of structural and electronic properties of Tl_xGa_(1-x)As alloys

The zincblende ternary alloys Tl_xGa_1-xAs (0<x<1) are studied by numerical analysis based on the plane wave pseudopotential method within the density functional theory and the local density approximation. To model the alloys, 16-atom supercells with the 2× 2× 2 dimensions are used and the dependency of the lattice parameter, bulk modulus, electronic structure, energy band gap, and optical bowing on the concentration x are analyzed. The results indicate that the ternary Tl_xGa_1-xAs alloys have an average band gap bowing parameter of 4.48 eV for semiconductor alloys and 2.412 eV for semimetals. It is found that the band gap bowing strongly depends on composition and alloying a small Tl content with GaAs produces important modifications in the band structures of the alloys.