This paper describes application of Sc-doped AlN (ScAlN) to wideband SAW devices in the 1 to 3 GHz range. First, it is shown theoretically that large SAW velocity and electromechanical coupling factor are simultaneously achievable when the ScAlN film is combined with a base substrate with extremely high acoustic wave velocities, such as diamond and SiC. Next, SAW delay lines are fabricated on the ScAlN/6H-SiC structure, and reasonable agreement between the theory and experiment is obtained. Finally, one-port SAW resonators are fabricated on the structure, and it is shown that high-performance is achievable in the 1 to 3 GHz range by use of the structure.

In this paper, the use of a structure comprising a thin LiNbO ₃ plate and a multilayered acoustic mirror composed of SiO ₂ and Pt for high-performance longitudinal leaky surface acoustic wave (LLSAW) device is proposed. The mirror is expected to offer a much higher reflectivity than that composed of SiO ₂ and AlN, which the authors proposed previously. The field distribution of these structures is calculated by using a finite element method. It is shown that the acoustic wave energy of the proposed structure is well confined in the vicinity of the top surface, and that leakage to the substrate is reduced. A one-port resonator is fabricated on the structure and its performance characteristics are evaluated. Owing to a high phase velocity of 6,035 m/s, which is about 1.5 times higher than that of conventional SAWs, a large impedance ratio of 71 dB was achieved at 3.5 GHz in addition to a large fractional bandwidth of 9.5%.

This article describes a new transverse edge structure with double busbar for surface acoustic wave (SAW) devices employing a 42°YX-lithium tantalate thin plate such as incredible high-performance (I.H.P.) SAW. This design offers good energy confinement and scattering loss suppression for a wide frequency range. First, preexisting transverse edge designs are reviewed, and their difficulties are pointed out using the dispersion relation for lateral SAW propagation. Then, numerical simulations are performed using the periodic 3-D finite-element method (FEM) powered by the hierarchical cascading technique, and effectiveness of the proposed structure is revealed. In addition, we also provide a possible solution to expand the frequency range giving well energy confinement and demonstrate effectiveness of manipulating the SAW slowness curve shape for transverse mode suppression.

This paper describes the development of a phase-sensitive laser probe with fast mechanical scan for RF surface and bulk acoustic wave (SAW/BAW) devices. The Sagnac interferometer composed of micro-optic elements was introduced for the selective detection of RF vertical motion associated with RF SAW/BAW propagation and vibration. A high-pass characteristic of the interferometer makes the measurement very insensitive to low-frequency vibration. This feature allows us to apply the fast mechanical scan to the interferometric measurement without badly sacrificing its SNR and spatial resolution. The system was applied to the visualization of a field pattern on the vibrating surface of an RF BAW resonator operating in the 2 GHz range. The field pattern was obtained in 17 min as a 2-D image (500 × 750 pixel with 0.4 μm resolution and SNR of 40 dB). The system was also applied to the characterization of an RF SAW resonator operating in the 1 GHz range, and the applicability of the system was demonstrated.

This paper describes application of the hierarchical cascading technique (HCT) to the 3D FEM analysis of transverse mode behaviors in surface acoustic wave (SAW) devices. Mirror cascading is proposed as a speed up technique for the HCT operation using the general purpose graphic processing unit (GPGPU). Two methods are implemented for the analysis; one is impedance calculation, and the other is calculation of SAW scattering coefficients at boundaries. It is demonstrated that HCT enables rapid calculation for successive simulation with scanning design parameters. Thus, techniques discussed in the paper are quite effective for optimization of device structures. It is also shown that GPGPU can accelerate HCT calculation dramatically, especially for 3D cases discussed in this paper.

This paper compares three different piston mode designs for temperature-compensated surface acoustic wave (TC-SAW) resonators using SiO ₂ /LiNbO ₃ structure. It was shown that in rough approximation, phase shift given by extra elements for the piston mode operation is determined by the total mass of extra elements and SiO ₂ which overlaid on piston region. The hammer head design without additional metal layers does not work properly due to the weaker impact of the extra elements when the SiO ₂ layer is thick. On the other hand, piston mode designs using metal dots or stripes are effective to suppress the transverse mode resonances even when the SiO ₂ layer is thick. Although larger metal thickness is preferable for the wideband operation, it also makes the split of main resonance. Thus, the optimal metal thickness can be found from this trade-off, and then the optimal metal width can be found to achieve good transverse mode suppression.