Elastic constants of the II-IV nitride semiconductors MgSiN2, MgGeN2 and MgSnN2

The single crystal elastic constants, polycrystalline elastic moduli and related properties of orthorhombic MgSiN2, MgGeN2 and MgSnN2 have been calculated using density functional theory and compared to the related wurtzite structured AIN, GaN and InN. Since there are no experimental studies of single crystal elastic properties of neither MgSiN2, MgGeN2 or MgSnN2, we have established the accuracy of the calculations by comparison with experimental data for MN, GaN and InN. The calculated polycrystalline elastic moduli of MgSiN2 are found to be in good agreement with available experimental elastic moduli. It will be shown that MgSiN2 and MgGeN2 have a small xy-plane lattice mismatch with AIN and GaN, respectively, while at the same time being significantly softer than both AIN and GaN. This shows that MgSiN2 and MgGeN2 should be possible to be grown on AIN and GaN without significant lattice mismatch or strain.