Coupled UHF Micromechanical Ring Resonators With Schottky Transducers

In this letter, we present ultra-high frequency coupled ring resonators realized in a suspended AlGaN/GaN heterostructure. The piezoelectric transducers consist of back-to-back nickel (Ni) Schottky diodes deposited on a 20-nm-thick AlGaN layer and a floating 2-D electron gas (2-DEG) sheet at the AlGaN/GaN interface. The dispersion characteristics of symmetric and anti-symmetric Lamb waves in ring resonators are characterized. Higher order resonance harmonics are targeted with very high mechanical quality factors (Qs) through optimized design of the coupling beam. Such a scheme minimizes the acoustic energy leakage to the substrate, and thus increases anchor Q. We report on a high-order breathing resonance mode at 900.7 MHz with very high mechanical Q of 8350 measured at room temperature and ambient pressure, achieving a record high frequency × Q value of 7.5 × 10
¹²
.