We report on an investigation of the structural and ferroelectric properties of ${\mathrm{Al}}_{1\text{–}x}{\mathrm{Sc}}_x\mathrm{N}$, ${\mathrm{Sc}}_y{\mathrm{Ga}}_x\mathrm{N}$ $(x+y=1)$, and quaternary ${\mathrm{Al}}_{1\text{–}x\text{–}y}{\mathrm{Sc}}_y{\mathrm{Ga}}_x\mathrm{N}$ alloys using density functional theory (DFT) calculations. The calculated spontaneous polarization $\left(P_{\mathrm{sp}}\right)$ and coercive field $\left(E_c\right)$ values for the ${\mathrm{Al}}_{1\text{–}x}{\mathrm{Sc}}_x\mathrm{N}$ and ${\mathrm{Sc}}_y{\mathrm{Ga}}_x\mathrm{N}$ $(x+y=1)$ ternary systems are in good agreement with experimental data, validating the computational approach. We find that the composition-induced structural transformation to the ferroelectric wurtzite phase in ${\mathrm{Al}}_{1\text{–}x}{\mathrm{Sc}}_x\mathrm{N}$ is strongly correlated with changes in the out-of-plane lattice parameter, while in ${\mathrm{Sc}}_y{\mathrm{Ga}}_x\mathrm{N}$ $(x+y=1)$, the transformation involves structural changes in both in-plane and out-of-plane lattice parameters. van der Waals interactions play a crucial role in accurately predicting the out-of-plane lattice parameters and, consequently, $P_{\mathrm{sp}}$. Our study of the quaternary alloys reveals regions in compositional space with reduced $E_c$, offering insights into the design of improved ferroelectric materials for next-generation electronic devices.

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• Electric polarization
• Ferroelectrics
• Density functional calculations
• Electronic structure