Evaluation of new single crystal piezoelectric materials for surface acoustic-wave applications

Surface acoustic waves (SAW), or Rayleigh waves, bound to the surfaces of piezoelectric materials are becoming rapidly significant in electronic device applications, particularly as VHF-UHF frequency filters and versatile time-domain processors. The majority of available devices utilize either signle crystalline quartz or lithium niobate as the piezoelectric medium. This paper describes briefly the growth and critical evaluation of SAW impedance and propagation properties for certain new single crystal piezoelectric materials. Crystals discussed are Czochralski-grown bismuth germanium oxide, films of zinc oxide and aluminum nitride both epitaxially grown on single crystal sapphire, and flux-grown beryllium oxide. It is concluded that bismuth germanium oxide may prove an important cost-effective alternative to both quartz and lithium niobate, and that either zinc oxide or aluminum nitride is destined to prove invaluable in the realization of monolithic circuits such as programmable tapped delay lines, in which SAW will be interfaced with metal-oxide semiconductor (large scale integrated) technology, and active SAW elements employing functional integration.