biostudies-literatureIzharUnited States Department of Defense | Defense Advanced Research Projects Agency (DARPA)United States Department of Defense | Defense Advanced Research Projects Agency19https://www.ebi.ac.uk/biostudies/studies/S-EPMC11754792biostudies-literatureUnknown11(1)Bulk Acoustic Wave (BAW) filters find applications in radio frequency (RF) communication systems for Wi-Fi, 3G, 4G, and 5G networks. In the beyond-5G (potential 6G) era, high-frequency bands (>8 GHz) are expected to require resonators with high-quality factor (Q) and electromechanical coupling ( kt2 ) to form filters with low insertion loss and high selectivity. However, both the Q and kt2 of resonator devices formed in traditional uniform polarization piezoelectric films of aluminum nitride (AlN) and aluminum scandium nitride (AlScN) decrease when scaled beyond 8 GHz. In this work, we utilized 4-layer AlScN periodically poled piezoelectric films (P3F) to construct high-frequency (~17-18 GHz) resonators and filters. The resonator performance is studied over a range of device geometries, with the best resonator achieving a kt2 of 11.8% and a Qp of 236.6 at the parallel resonance frequency ( fp ) of 17.9 GHz. These resulting figures-of-merit are ( FoM1=kt2Qp and FoM2=fpFoM1×10-9 ) 27.9 and 500, respectively. These and the kt2 are significantly higher than previously reported AlN/AlScN-based resonators operating at similar frequencies. Fabricated 3-element and 6-element filters formed from these resonators demonstrated low insertion losses (IL) of 1.86 and 3.25 dB, and -3 dB bandwidths (BW) of 680 MHz (fractional BW of 3.9%) and 590 MHz (fractional BW of 3.3%) at a ~17.4 GHz center frequency. The 3-element and 6-element filters achieved excellent linearity with in-band input third-order intercept point (IIP3) values of +36 and +40 dBm, respectively, which are significantly higher than previously reported acoustic filters operating at similar frequencies.Microsystems & nanoengineeringPeriodically poled aluminum scandium nitride bulk acoustic wave resonators and filters for communications in the 6G era.PMC11754792HR0011221-9-0037IzharLeathersich JKochhar AMoe CYao SDu XStach EAVetury RMusavigharavi PFiagbenu MMADeng YOlsson RHfalsePeriodically poled aluminum scandium nitride bulk acoustic wave resonators and filters for communications in the 6G era.Bulk Acoustic Wave (BAW) filters find applications in radio frequency (RF) communication systems for Wi-Fi, 3G, 4G, and 5G networks. In the beyond-5G (potential 6G) era, high-frequency bands (>8 GHz) are expected to require resonators with high-quality factor (Q) and electromechanical coupling ( kt2 ) to form filters with low insertion loss and high selectivity. However, both the Q and kt2 of resonator devices formed in traditional uniform polarization piezoelectric films of aluminum nitride (AlN) and aluminum scandium nitride (AlScN) decrease when scaled beyond 8 GHz. In this work, we utilized 4-layer AlScN periodically poled piezoelectric films (P3F) to construct high-frequency (~17-18 GHz) resonators and filters. The resonator performance is studied over a range of device geometries, with the best resonator achieving a kt2 of 11.8% and a Qp of 236.6 at the parallel resonance frequency ( fp ) of 17.9 GHz. These resulting figures-of-merit are ( FoM1=kt2Qp and FoM2=fpFoM1×10-9 ) 27.9 and 500, respectively. These and the kt2 are significantly higher than previously reported AlN/AlScN-based resonators operating at similar frequencies. Fabricated 3-element and 6-element filters formed from these resonators demonstrated low insertion losses (IL) of 1.86 and 3.25 dB, and -3 dB bandwidths (BW) of 680 MHz (fractional BW of 3.9%) and 590 MHz (fractional BW of 3.3%) at a ~17.4 GHz center frequency. The 3-element and 6-element filters achieved excellent linearity with in-band input third-order intercept point (IIP3) values of +36 and +40 dBm, respectively, which are significantly higher than previously reported acoustic filters operating at similar frequencies.2025-01-01T00:00:00Z2025 Jan2025-04-05T00:26:13.973Z2025-04-05T00:26:13.973ZS-EPMC117547923984343110.1038/s41378-024-00857-4