Alloying aluminum nitride with molybdenum could significantly enhance its electromechanical coupling constant.

Aluminum nitride (AlN) has been widely used in bandpass filters for wireless communication applications, but its low electromechanical coupling factor (k t 2 ) limits the bandwidth of the filter based on it. In this work, AlN alloys incorporated with various transition metals are theoretically studied, and Mo-alloy AlN (Mo x Al 1−x N) is predicted to be more prominent in improving k t 2 . Furthermore, the influence of Hubbard U correction on the k t 2 of Mo x Al 1−x N is discussed, and the correction is found to show a crucial role at a high x. The magnitude of k t 2 is more correlated with the piezoelectric stress constant e 33 , and both of them depend on the distribution of Mo atoms. The contribution of each atom to piezoelectric performance is described by an effective displacement-response internal-strain parameter Γ 33 in this work, which is generally proportional to internal parameter u and response of u to applied strain along the z -axis. The increase of k t 2 is ascribed to the Mo-induced larger u and Γ 33 , but the Mo dimer and line along the z-axis weaken the increase mechanism. To obtain a high k t 2 , it is better to alloy Mo atoms into more sublayers of AlN and with fewer Mo dimers and lines along the z -axis. The behavior that the Mo atoms distributed evenly in the xy plane is also beneficial. A high k t 2 of 37.8% is predicted in a special quasirandom configuration of Mo 0.167 Al 0.833 N, which might be the highest value reported to date for the AlN alloys. [Display omitted] • Mo-alloy AlN outperforms other alloys in enhancing the k t 2 of AlN. • A high k t 2 of 6.87 times that of pure AlN is predicted. • The magnitude of k t 2 depends on the distribution of Mo atoms in Mo x Al 1−x N. • Γ 33 is used for the first time to explain the contribution of each atom to k t 2 . [ABSTRACT FROM AUTHOR]