First-principles investigation of BAs and Bx Ga1−x As alloys

Using first-principles calculations in the generalized gradient approximation, the electronic properties of BAs and BxGa1–xAs alloys are studied. At the Brillouin-zone centre, the lowest conduction band is the three-degenerate p-like Γ15c state rather than s-like Γ1c state, and the conduction band minimum (CBM) is along the Δ line between the Γ and X points-at approximately 11/14(1,0,0)2π/a. With boron content at 0%–18.75%, BxGa1–xAs alloys have a small (2.6 eV) and relatively composition-independent band-gap bowing parameter, the band-gap increases monotonically by ∼18meV/B% with increasing boron content. In addition, the formation enthalpies of mixing for Bx Ga1–xAs alloys with boron content at 6.25% and 12.5% are calculated, and the large formation enthalpies may explain the difficulty in alloying boron to GaAs. (condensed matter: electronic structure, electrical, magnetic, and optical properties)