QUASI-PARTICLE ENERGIES FOR CUBIC BN, BP, AND BAS

Electronic excitation energies at the high-symmetry points GAMMA, X, and L are obtained for zinc-blende-structure BN, BP, and BAs in the GW approximation using a model dielectric function. A model for the static screening matrix makes use of the ab initio ground-state charge density and either experimental values or empirical estimates for epsilon-infinity, the electronic contribution to the macroscopic dielectric constant. Wave functions from an ab initio local-density-approximation calculation with norm-conserving pseudopotentials are employed along with the self-consistent quasiparticle spectrum to obtain the energy-dependent one-particle Green function G. The minimum band gaps are found to be 6.3, 1.9, and 1.6 eV for BN, BP, and BAs, respectively, in close agreement with existing measurements of 6.1 and 2.0 eV for BN and BP, respectively. The BN direct band gap is predicted to be 11.4 eV versus the experimental value of 14.5 eV, and the BP direct band gap is predicted to be 4.4 eV versus 5.0 eV from experiment.