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

TL;DR

This paper demonstrates a high-frequency, sub-micron wavelength phononic cavity in GaN-on-Sapphire with high quality factors, suitable for quantum information processing and hybrid quantum devices.

Contribution

The development of a high-frequency traveling-wave phononic cavity in GaN with enhanced quality factors and potential for integration with quantum systems.

Findings

Achieved up to 5 GHz frequency in GaN-on-Sapphire

Quality factor increased from 5,000 at room temperature to 30,000 at 7 K

Frequency-quality factor product of 1.5×10^{14}

Abstract

Thin-film gallium nitride (GaN) as a proven piezoelectric material is a promising platform for the phononic integrated circuits, which hold great potential for scalable information processing processors. Here, an unsuspended traveling phononic resonator based on 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 was found when temperature decreases from room temperature ($Q=5000$) to $7\,\mathrm{K}$ ($Q=30000$) and thus a frequency-quality factor product of $1.5\times10^{14}$ is obtained. Higher quality factors are available when the fabrication process is further optimized. Our system shows great potential in hybrid quantum devices via circuit quantum acoustodynamics.