Structural, electronic and optical properties of II-IV-N-2 compounds (II = Be, Zn; IV = Si, Ge)

A detailed study of structural, electronic and optical properties of II-IV-N-2 ternary compounds (II = Be, Zn; IV = Si, Ge) has been performed by means of ab initio density functional theory calculations. The germanium containing compounds were found to be direct-gap semiconductors with gaps of 3.37 eV and 1.67 eV for BeGeN2 and ZnGeN2, respectively, with oscillator strength of direct transition comparable to GaN. Two other silicon containing compounds are characterized by indirect gaps of 5.19 (3.32) eV for BeSiN2 (ZnSiN2). Crystal structure being orthorhombic and lattice parameters for BeSiN2 and ZnSiN2 are in good agreement with the available experimental data.