Quasiparticle self-consistent GW electronic band structures of Be-IV-N2 compounds

Abstract

The electronic band structures of BeSiN2 and BeGeN2 compounds are calculated using the quasiparticle self-consistent GW method. The lattice parameters are calculated for the wurtzite based crystal structure commonly found in other II–IV-N2 compounds with the Pbn21 space group. They are determined both in the local density approximation and generalized gradient approximation, which provide lower and upper limits. At the GGA lattice constants, which gives lattice constants closer to the experimental ones, BeSiN2 is found to have an indirect band gap of 6.88 eV and its direct gap at is 7.77 eV, while in BeGeN2 the gap is direct at and equals 5.03 eV. To explain the indirect gap in BeSiN2 comparisons are made with the parent III-N compound w-BN band structure. The effective mass parameters are also evaluated and found to decrease from BeSiN2 to BeGeN2.