Abstract: Bulk acoustic wave resonators are presented. Such resonators typically operate based on a dynamic nonuniform effective piezoelectricity in composite multilayer ferroelectrics with large electrostriction coefficients, like barium strontium titanate (BST). Harmonic resonance modes of a multilayer bulk acoustic wave resonator can be selectively excited with an electromechanical coupling coefficient equal to the fundament mode, which is contrary to the trend K2?1/n2 exhibited by conventional piezoelectric bulk acoustic resonators. Such a resonator allows for the design of a new class of band-switching filters.

Abstract: Tunable capacitors based on scandium aluminum nitride (ScAlN) are disclosed. In one aspect, a tunable capacitor or varactor may be formed from a ferroelectric material. More particularly, the ferroelectric material may be formed from ScAlN. The permittivity of the ScAlN material may be adjusted using a direct current (DC) electric field applied to the material. Tunable capacitors or varactors have myriad uses in wireless communication systems, such as being used in filters or transformers. Further, use of ScAlN allows resonators and varactors to be formed on the same die or wafer using the same process flow, thereby reducing cost, fabrication complexity, and also potentially reducing the overall size of the circuit.

Abstract: A ferroelectric acoustic resonator structure is provided. The tunable ferroelectric acoustic resonator structure is configured to resonate in a series resonance frequency to pass a signal from a signal input to a signal output and block the signal in a parallel resonance frequency by presenting an equivalent parallel capacitance between the signal input and the signal output. The series resonance frequency can be tuned by applying a voltage to polarize the tunable ferroelectric acoustic resonator structure. However, the voltage can also cause an increase in the equivalent parallel capacitance to therefore shift the parallel resonance frequency toward the series resonance frequency. Herein, the tunable ferroelectric acoustic resonator structure is configured to reduce the equivalent parallel capacitance that is increased when tuning the series resonance frequency.

Abstract: Reconfigurable bulk acoustic wave (BAW) devices include one or more ferroelectric materials as the transduction layer(s). A polarization state of at least one of the ferroelectric material(s) is adjusted by applying a bias voltage across electrodes of the BAW device. The application of the bias voltage can change one or more properties of the ferroelectric material, which in turn may change a response of the BAW device.

Abstract: A ferroelectric acoustic resonator structure is provided. The tunable ferroelectric acoustic resonator structure includes a pair of ferroelectric acoustic resonator networks coupled in parallel between a signal input and a signal output. The ferroelectric acoustic resonator networks are tuned by a pair of pulse voltages to resonate in a desired series resonance frequency. However, the pair of pulse voltages can change an equivalent capacitance to therefore cause a parallel resonance frequency of the tunable ferroelectric acoustic resonator structure to shift. Herein, the pair of pulse voltages are determined to cause one of the ferroelectric acoustic resonator networks to increase the equivalent capacitance and to cause another one of the ferroelectric acoustic resonator networks to decrease the equivalent capacitance by an equal amount.

Abstract: The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator, which includes a bottom electrode, a top electrode structure, and a multilayer transduction structure sandwiched therebetween. Herein, the multilayer transduction structure is composed of multiple transduction layers, at least one of which is formed of a ferroelectric material with a box-shape polarization-electric field curve. Each transduction layer includes a transduction border (BO) portion positioned at a periphery of a corresponding transduction layer and a transduction central portion surrounded by the transduction BO portion. A combination of all transduction BO portions forms a transduction BO section of the multilayer transduction structure, and a combination of all transduction central portions forms a transduction central section of the multilayer transduction structure.

Abstract: The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator, which includes a bottom electrode, a top electrode structure, and a ferroelectric layer sandwiched in between. Herein, the ferroelectric layer is formed of a ferroelectric material, which has a box-shape polarization-electric field (P-E) curve. The ferroelectric layer includes a ferroelectric border (BO) portion positioned at a periphery of the ferroelectric layer and a ferroelectric central portion surrounded by the ferroelectric BO portion. The ferroelectric BO portion has a first polarization and a first electromechanical coupling coefficient, and the ferroelectric central portion has a second polarization and a second electromechanical coupling coefficient. An absolute value of the first polarization is less than an absolute value of the second polarization, and the first electromechanical coupling coefficient is less than the second electromechanical coupling coefficient.

Abstract: The present disclosure relates to a Bulk Acoustic Wave (BAW) resonator with tunable electromechanical coupling. The disclosed BAW resonator includes a bottom electrode, a top electrode, and a multilayer transduction structure sandwiched therebetween. Herein, the multilayer transduction structure is composed of multiple transduction layers, and at least one of the transduction layers is formed of a ferroelectric material, whose polarization will vary with an electric field across the ferroelectric material. Upon adjusting direct current (DC) bias voltage across the bottom electrode and the top electrode, an overall polarization of the multilayer transduction structure and an overall electromechanical coupling coefficient of the multilayer transduction structure are capable of being changed.

Abstract: Bulk acoustic wave resonators are presented. Such resonators typically operate based on a dynamic nonuniform effective piezoelectricity in composite multilayer ferroelectrics with large electrostriction coefficients, like barium strontium titanate (BST). Harmonic resonance modes of a multilayer bulk acoustic wave resonator can be selectively excited with an electromechanical coupling coefficient equal to the fundament mode, which is contrary to the trend K2?1/n2 exhibited by conventional piezoelectric bulk acoustic resonators. Such a resonator allows for the design of a new class of band-switching filters.