Ferroelectric polarization and piezoelectric properties in orthorhombic Zn₃WN₄ and Zn₃MoN₄: An atomic sublattice decomposition

Metal-doped AlN (i.e., Al_1−xSc_xN) has emerged as a promising ferroelectric material due to its excellent compatibility with conventional Si semiconductors. Understanding how individual cations contribute to the overall ferroelectric polarization and piezoelectric response is crucial for the rational design of high-performance devices. In this work, we take the recently synthesized wurtzite-derived ternary nitrides Zn₃MN₄ (M = W, Mo) as an example and employ first-principles calculations to investigate the atomic sublattice decomposition of their ferroelectric polarization and longitudinal piezoelectric coefficient. Our results reveal that the polarization value in Zn₃MN₄ is primarily dominated by the more electronegative W/Mo cation due to the strong hybridization between W 5dz^2/Mo 4dz² and N 2p orbitals. Furthermore, the piezoelectric coefficient e₃₃ is primarily governed by the bond between the more electronegative W/Mo cation and the N anion within the MN₄ tetrahedron along the c axis. This is attributed to the large absolute value of Born effective charge and (Formula presented.) of the N atom at the tetrahedral vertex along the c direction. We further confirm that these findings can be extended to other wurtzite-derived ternary nitrides with different chemical formulas. Our study provides valuable theoretical insights for the future experimental design of wurtzite nitride semiconductors with excellent ferroelectric and piezoelectric properties.