Theoretical evidence for enhanced piezoelectric properties for BY- or NaV-codoped wurtzite AlN

Abstract

Enhancing the piezoelectric properties of wurtzite aluminum nitride (w-AlN) without compromising its structural stability presents a significant experimental and theoretical challenge. This study employs first-principles calculations to comprehensively investigate the structural stability and piezoelectric properties of w-AlN codoped with BY-and NaV-.Analyses of formation enthalpy, phonon spectra, and AIMD Molecular Dynamics simulation demonstrate that the ordered alloy structure possesses better stability. The results confirm that the conventional ordered codoped configuration is energetically more favorable than its disordered counterpart. It was successfully predicted that the piezoelectric coefficients of (BY)xAl1-xN and (NaV)xAl1-xN alloys would be several times higher than that of pure wurtzite AlN. Among them, when the doping concentration reaches 50%, the piezoelectric strain constant d33 of (NaV)0.5Al0.5N (22.37 pC/N) is 1.7 times that of (BY)0.5Al0.5N (13.26 pC/N), and it reaches 5.4 times that of pure AlN (4.14 pC/N). The findings reveal that the enhanced polarization along the z-axis in (NaV)xAl1-xN results primarily from significant charge redistribution and lattice distortion induced by doping. In addition, another reason for the increase of piezoelectric strain constant d33 is the weakening of Al-N covalent bond sum. This work offers a theoretical foundation for advancing the piezoelectric performance of w-AlN films, paving the way for their use in high-sensitivity sensor and acoustic device applications.