Ultra-high Q monocrystalline silicon carbide disk resonators anchored upon a phononic crystal

Abstract

This work introduces a 3D design incorporating a phononic crystal to decouple a centrally-supported silicon carbide bulk acoustic wave disk resonator from its Si handle layer. By overcoming thermoelastic and anchor losses in bulk acoustic wave resonators, this scheme allows for probing the phonon-phonon dissipation limits i.e. Akhiezer loss. Using a custom silicon carbide on insulator platform, SiC disk resonators anchored upon phononic crystal were fabricated and optically measured. SiC disk resonators exhibit Q-factors near 4M with a record f·Q product of 1.85x1013 Hz for the radial breathing mode operating at 5 MHz, limited by thermoelastic losses. This is the highest f·Q measured in monocrystalline silicon carbide resonators, an important step toward the batch fabrication of inertial-grade SiC BAW gyroscopes.