Ternary alloys formed by adding transition metals scandium and yttrium to aluminum nitride have been shown to have enhanced ferroelectric and piezoelectric properties that enable new functional capabilities in electronic and optoelectronic devices. Moreover, incorporating boron into aluminum nitride can lead to a significant increase in the spontaneous polarization and strong ferroelectric properties. Although these alloys have been experimentally synthesized, their growth is particularly challenging. Furthermore, the differing crystal structures of the parent binary compounds lead to phase segregation phenomena that make it impossible to grow the alloys in one specific crystal modification over the entire composition range. As a result, there is a lack of understanding of the fundamental properties of these alloys, particularly regarding the piezoelectric characteristics. In this work, we employ a density functional theory-based approach to study the structural and elastic properties of these three alloys. We calculate the lattice constants, the internal parameter, and the Poisson's ratios for the full range of compositions in these alloys in order to identify where phase segregation may occur. Furthermore, we study their piezoelectric properties by first evaluating the spontaneous polarization and subsequently the piezoelectric stress and strain coefficients as a function of composition. To validate the theoretical model, we compare the calculated values with the experimental data available for some of the alloy compositions. Finally, we provide parametric expressions for the structural and piezoelectric properties, which can be used for device design.

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• Piezoelectricity
• Structural properties
• Ferroelectrics
• Semiconductors
• Wide band gap systems
• Density functional theory
• First-principles calculations