Surface acoustic wave properties of ZnO films on [100]-cut [110]-propagating GaAs substrates

GaAs is employed as a material for ACT devices because it is a piezoelectric semiconductor. The use of a ZnO film on top of the ACT substrate to enhance the piezoelectric coupling is investigated. The ZnO film structure makes it possible to construct monolithic devices with ordinary surface acoustic wave (SAW) devices and GaAs electronics. In order to provide a basis for the design of such devices, the authors report surface acoustic wave properties, including effective piezoelectric coupling constant, slowness surface, and propagation loss, measured on sputtered ZnO film overlayed {100}-cut <110> -propagating GaAs substrates. The measurements are performed on different thicknesses of the film over the range of 1.6-4.0 μm and with films of different grain sizes. Interdigital transducers (IDTs) operating between 180 and 360 MHz are fabricated, and a knife-edge laser probe is used to measure the SAW propagation. The measured data are compared with theoretical values