High-Q cryogenic surface acoustic wave resonators in the GHz range

Surface acoustic wave (SAW) resonators provide a compact platform for confining microwave-frequency phonons and are widely used in radio frequency technologies, but their operation at gigahertz frequencies and cryogenic temperatures remains challenging. In this regime, conventional design rules do not directly apply, and achieving high-quality acoustic confinement requires careful consideration about geometry and loss mechanisms. Here, we present a systematic experimental study of SAW resonators on gallium arsenide (GaAs), a platform of particular interest for hybrid quantum devices but comparatively unexplored for high-Q SAW cavities. By varying design parameters such as cavity length, wavelength, and crystal orientation, we study resonator performance and achieve quality factors up to 28'000 in the gigahertz range for the longest investigated resonator, identifying cavity length as a key parameter. In addition, we introduce mesa steps within the acoustic cavity, mimicking realistic device architectures and providing insight into scattering processes and additional dissipation channels. Our results establish practical design guidelines for GaAs-based SAW resonators and support their development as a scalable platform for quantum acoustics and phonon-mediated hybrid systems.