Electronic band structure, crystal structure and phonons of ZnSiN$_2$

ZnSiN$_2$ is an interesting alternative to GaN. Its crystal structure is derived from the wurtzite structure of GaN by a particular ordered subsitution of the Ga atoms by Zn and Si in such as way that each N is coordinated with two Si and two Zn atoms. Electronic structure calculations were performed with two different approaches, the plane-wave ultrasoft pseudopotential approach and the full-potential linearized muffin-tin orbital method both using the local density approaximation (LDA). The structure was fully optimized. The relaxation consists primarily of the N atom finding its optimum position inside its nearest neighbor tetrahedron by making a shorter Si-N and longer Zn-N bond. An indirect LDA band gap of about 3.4 eV is obtained. Thus a gap larger than for GaN is expected. Calculations of the phonons at the center of the Brillouin zone are in progress using the linear response approach. A comparison with ZnGeN2, which was studied earlier, [W. R. L. Lambrecht et al. Phys Rev. B 72, 155202 (2005)] will be presented.