Dynamic Mode Suppression and Frequency Tuning in S-Band GaN/YIG Magnetoelastic HBARs

This work presents the detailed characterization and analysis of recently reported magnetoelastic high-overtone bulk acoustic resonators (ME-HBARs), which are multimode RF-acoustic (phononic) resonators operating in the
${S}$
-band. These unique devices are fabricated by microtransfer printing (MTP) piezoelectric GaN transducers onto a ferrimagnetic yttrium iron garnet (YIG) substrate. The YIG substrate also supports spin waves (magnons) when biased with an external magnetic field. The resulting phonon–magnon hybridization can be used to suppress or tune the acoustic modes of the ME-HBAR. The experiment spans 66 distinct acoustic resonance modes from 2.4 to 3 GHz, each of which can be suppressed or tuned as much as ±6 MHz, with a bias magnetic field
$\le 0.21$
T. The experimental ME-HBAR data show good agreement with analytical modeling of the magnetoelastic hybridization in YIG. Such ME-HBARs can be used as dynamically tunable or switchable resonators, oscillators, comb filters, or frequency selective limiters in RF signal processing subcomponents. By integrating incompatible materials (YIG, epitaxial GaN) and disparate functionalities (spin waves, acoustic waves) into one hybrid multidomain system, this work also demonstrates the power and broad scope of the MTP technique.