A ladder filter includes a plurality of series resonators and a plurality of shunt resonators connected between an input port and an output port. At least one of the series or shunt resonators include a bulk acoustic wave (BAW) resonator structure, which includes: a first electrode disposed over a substrate; an air cavity located in the substrate and below the first electrode; a piezoelectric layer disposed over the first electrode and comprising aluminum scandium nitride, the piezoelectric layer having a thickness in a range of approximately 1.0 microns to approximately 1.5 microns; and a second electrode disposed over the piezoelectric layer. The BAW resonator structure has an area, and the area is less than an area of a comparable BAW resonator structure comprising identical layers and materials except for an undoped aluminum nitride piezoelectric layer.