Impedance-matched high-overtone bulk acoustic resonator

Abstract

We demonstrated a nearly impedance-matched high-overtone bulk acoustic resonator (HBAR) operating at super high frequency ranges using an epitaxial AlN piezoelectric layer directly grown on a conductive SiC cavity substrate with no metal layer insertion. The small impedance mismatch was verified from the variation in the free spectral range (FSR); the experimentally obtained FSR spectra were greatly reproduced using the Mason model. Broadband phonon cavity modes up to the K-band (26.5 GHz) were achieved at an AlN layer thickness of 200 nm. The high figure of merit of [Formula: see text] at 10 GHz was also obtained. Our nearly impedance-matched high-quality HBAR will enable the development of microwave signal processing devices for 5G and future 6G communication systems, such as low-phase noise oscillators and acoustic filters, as well as research on high-frequency acoustic systems hybridized with electric, optical, and magnetic systems.

Observation of Photodielectric Effect in Aluminum Nitride Piezoelectric Films

“…Aluminum nitride (AlN) films have been applied in a number of important areas such as ultraviolet photodetectors, − nonlinear optical devices, , microelectro-mechanical systems (MEMS) devices, − and acoustic wave filters − due to their high-temperature stability, large sound velocity, superior piezoelectric response, and compatibility with the complementary metal-oxide-semiconductor (CMOS) processing. Previous studies were primarily focused on compositional and structural tuning for the enhanced piezoelectric responses in AlN films, but limited attention has been given to the photoinduced dielectric properties.…”