Electronic structure, dynamic stability, elastic, and optical properties of Mg TM N2(TM = Ti, Zr, Hf) ternary nitrides from first-principles calculations

Abstract

Ternary nitride semiconductors with tunable electronic structure and charge transport properties have attracted increasing attention as optoelectronic materials. The recently discovered ternary Mg T M N 2 (T M = Ti, Zr, Hf) are predicted to be nondegenerate semiconductors with visible-range optical absorption onsets. In the present study, the electronic structure, elastic properties, optical absorption spectrum, and dynamic stability of the Mg T M N 2 system have been systematically studied by first-principles calculations based on the density functional theory. These compounds show semiconductor characteristics with a bandgap ranging from 1.0 to 1.5 eV predicted by the Heyd-Scuseria-Ernzerhof approach. Compared to the traditional semiconductors of Si and GaAs and III-V nitrides of GaN and AlN, these ternary nitrides have stronger resistance to external compression, shear strain, and deformation due to the larger elastic modulus. MgTiN 2 shows a strong anisotropy characteristic along the x y plane and z axis, while for MgZrN 2 and MgHfN 2, a weak elastic anisotropy is predicted. The absorption regions of these compounds are mainly concentrated in the ultraviolet region, and MgTiN 2 is more sensitive to visible light with respect to the other two compounds. The thermodynamic stability of MgTiN 2, MgZrN 2, and MgHfN 2 is verified by the stable phonon dispersion relations. It is found that the most stable low Miller index surface is (110) for MgTiN 2 and (100) for MgZrN 2 and MgHfN 2.