Piezoelectric, dielectric and polarization properties of AlBN

AlN is a material of great importance for acoustic-wave devices and micro-electromechanical systems due to its polar wurtzite structure resulting in strong spontaneous polarization and piezoelectricity. Recently, it has been observed that alloying B into AlN leads to enhanced piezoelectricity, ferroelectricity, and higher dielectric permittivity, which could enable new functionalities and applications. In this work, we employ density functional theory calculations to investigate the spontaneous and piezoelectric polarization of AlBN alloys, using both the virtual crystal approximation and the supercell method. Enhanced piezoelectricity and ferroelectricity are observed in AlBN because of the increase in ionic bonding character as well as the phase transition from the wurtzite to the layered-hexagonal structure. We also carry out a systematic study of the dielectric permittivity of AlBN solid solutions to explore the enhanced dielectric properties in this system.