Ab-initio electronic structure calculations and properties of [SixSn1 − x]3N4 ternary nitrides

Abstract

We carry out ab initio electronic structure calculations of (SixSn1−x)3N4 using density functional theory with projector augmented-wave potentials under the generalized gradient approximation. We find that the energetically favorable structure of Sn3N4 is the face-centered cubic spinel structure, followed by the hexagonal structure which has energy band gaps of 1.85eV and 1.44eV respectively. The (SixSn1−x)3N4 ternary compound can exhibit both cubic and hexagonal crystal structures over the full range of x. However, the cubic structure is found to be energetically favorable for x<0.3 above which the hexagonal structure of (SixSn1−x)3N4 dominates. The energy band gap can be tuned continuously from 1.44eV up to 5.8eV in the case of the hexagonal crystal structure of (SixSn1−x)3N4 and from 1.85eV to 4.82eV in the case of cubic (SixSn1−x)3N4. Nevertheless the energy gap of (SixSn1−x)3N4 is direct only for x<0.3 when it is cubic and for x<0.5 when hexagonal.