High-frequency traveling-wave phononic cavity with sub-micron wavelength

Abstract

Thin-film gallium nitride (GaN) is a promising platform for phononic integrated circuits that hold great potential for scalable information processing processors. Here, an unsuspended traveling phononic resonator based on a high-acoustic-index-contrast mechanism is realized in GaN-on-Sapphire with a frequency up to 5 GHz, which matches the typical superconducting qubit frequency. A sixfold increment in quality factor is found when temperature decreases from room temperature ( Q =  5000) to [Formula: see text] ( Q =  30 000), and thus, a frequency-quality factor product of [Formula: see text] is obtained. Higher quality factors should be available when the fabrication process is further optimized. Our system shows great potential in hybrid quantum devices via the so-called circuit quantum acoustodynamics.