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 ≤ 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.

Passive High Power RF Comb Filters Using Epitaxial GaN/NbN/SiC HBARs.

This report presents the first demonstration of passive RF comb filters made using epitaxial GaN/NbN/SiC high overtone bulk acoustic resonators (epi-HBARs). The two-port device is fabricated on electronic-grade GaN, electrically transduced, and acoustically coupled. The multi-mode epi-HBAR comb filter demonstrated here has 158 sharp filter passbands periodically distributed between 1 and 4 GHz (L-S-bands) with a free spectral range (FSR) of 17 MHz. The individual passbands of the epi-HBAR comb filter demonstrate transmission bandwidths (BWs) up to 800 kHz, f × Q values of up to 7×1014 Hz, and an average [Formula: see text] figure of merit of 41.2 at room temperature. The GaN/NbN/SiC epi-HBAR comb filter is capable of operating at high RF power levels, with linear and distortion-free performance seen up to at least 1 W of continuous wave (CW) power and up to at least 10 W of pulsed power. The compact epi-HBAR comb filters can be co-fabricated with GaN-based electronics and could potentially replace larger, off-chip or discrete-component comb filters. They can be used for spectrum sensing and as signal processing elements for remote sensing and pulsed radar.