Dynamic mode suppression and frequency tuning in S-band GaN/YIG magnetoelastic HBARs

This work presents detailed characterization and analysis of recently reported magnetoelastic high overtone bulk acoustic resonators (ME-HBARs), which are multi-mode RF-acoustic (phononic) resonators operating in the S-Band. These unique devices are fabricated by micro-transfer 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 GHz to 3 GHz, each of which can be suppressed or tuned as much as ± 6 MHz, with a bias magnetic field ≤ 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 sub-components. By integrating incompatible materials (YIG, epitaxial GaN), and disparate functionalities (spin waves, acoustic waves), into one hybrid multi-domain system, this work also demonstrates the power and broad scope of the MTP technique.