Large piezoelectric and elastic properties in B and Sc codoped wurtzite AlN

Balancing the piezoelectric stress coefficient ( e 33 ) and the elastic constant ( C 33 ) of AlN-based materials is challenging but crucial for its application in bulk acoustic wave resonators. In this work, via first-principles calculations, we demonstrate that e 33 and C 33 can be simultaneously enhanced by adding boron (B) in the Sc x Al 1−x N system. Compared with Sc x Al 1−x N, the large C 33 in B 0.125 Sc x−0.125 Al 1−x N is caused by the shorter and stiffer B–N bonds, and the enhancement of e 33 mainly comes from a larger sensitivity of atomic coordinates with respect to the strain [Formula: see text]. Further investigation shows that the introduction of B in Sc x Al 1−x N significantly decreases the ratio of lattice parameter c over a due to the planar coordination preference of bulk BN, which is accompanied by an increased average [Formula: see text] and e 33 . Such a negative correlation can be attributed to the fact that [Formula: see text] of N is proportional to the asymmetry of transversal bond strengths but inversely proportional to the overall average bond strengths around N atoms. Such a bonding character observed in this work could be beneficial to the design of wurtzite materials with large piezoelectric coefficients and high elastic constants.