1.02 GHz cross-sectional Lamé mode resonator with high KT2 exceeding 4.6%

This paper demonstrates a new class of AlN-based piezoelectric resonators for operation in the microwave frequency range. These novel devices are identified as Cross-Sectional-Lamé-Mode resonators (CLMRs) as they rely on the piezoelectric transduction of a Lamé mode, in the cross-section of an AlN plate. Such 2-dimensional (2D) mechanical mode of vibration, characterized by motion along both the lateral and the thickness directions, is actuated and sensed piezoelectrically through the coherent combination of the en and en piezoelectric coefficients of AlN. This special feature enables the implementation of CLMRs with high values of electromechanical coupling coefficient (kt2). We demonstrate a kt2 value in excess of 4.6% in a CLMR operating around 1.02 GHz. Such kt2 value is the highest ever reported among AlN resonators employing interdigital-metal-electrodes (IDTs) to actuate and to sense the mechanical motion.