Light interaction with AlN-based SAW device fabricated on flexible and silicon substrate

The electroacoustic photoresponse of surface acoustic wave (SAW) delay line device, based on piezoelectric aluminum nitride (AlN) thin film sputtered on silicon rigid substrate and flexible polyethylene naphthalate (PEN) substrate, has been investigated. The electroacoustic response of SAW devices has been analyzed by measuring the transfer function S
₂₁
under light stimulus of different wavelengths. The S
₂₁
out-of-band insertion loss of SAW devices fabricated on silicon is strongly influenced by the photovoltaic effect when the devices are stimulated by light. A mathematical model has been implemented to correlate the out-of-band loss with the material's electrical admittance. The frequency shift of the resonance frequency modes (Rayleigh and Lamb) has also been characterized for both SAW devices on silicon and PEN substrates, when exposed to UV light. To the best of our knowledge, this is the first detection of UV light by a flexible AlN based SAW device. Further development of these devices exploiting electroacoustic photoresponse phenomena could lead to a new class of remote SAW devices as light sensors in the range between UV to IR.