Hypersonic Surface Phononic Bandgap Demonstration in a CMOS-Compatible Pillar-Based Piezoelectric Structure on Silicon

The promise of surface phononic crystals (PnCs) for $e.g.$ rf signal processing in wireless communication (like your mobile phone) has not been realized, due to the complexity of acoustic wave propagation in such structures, plus the lack of a low-loss, CMOS-compatible platform. The authors identify a wide, hypersonic surface phononic band gap in a pillar-based surface PnC. The significance of their platform lies in the reduced phononic material loss in dielectric pillars, and the use of CMOS-compatible AlN. This allows dense integration of low-loss hypersonic devices with electronics on the same die, enabling many exciting applications of surface PnCs.