A new approach to enhance the sensitivity of existing SAW UV-visible photo-detectors based on the monitoring of the multiple reflections of the acoustic waves in the Fourier transform of the frequency response (S21) is demonstrated. By using this concept, it is possible to monitor the UV-visible light in a wide intensity range from very high to ultralow. We present a strategy to obtain an ultrafast SAW UV photo-detector with millisecond response by tuning the deposition conditions of the ZnO film and using the multiple-reflections concept.

Optical, structural and photo-electric properties of Zn 1−x−y Mg x Al y O films on piezoelectric LiNbO 3 substrates prepared by PLD method at varied temperatures are studied. The ZnO band gap is enlarged to ∼5 eV by Mg atoms dosing. The reduced growth temperature of 400 °C results in lower conductivity of the film. The films grown at 400 °C-500 °C show deep UV photoelectrical response of 0.1-0.2 ms which is 50-100 times faster compared to devices based on films produced at 600 °C with higher crystallinity. By moderate Al doping and varying the temperature of Zn(Mg, Al)O film growth one may tune the initial sheet conductivity, i.e. the 'working point' of UV SAW detector, to the abrupt slopes of Γ(σ) characteristics, thus, optimizing the sensor sensitivity and response time. The UV 'light on/off' sheet conductivity change Δσ/σ dark , defining the sensitivity of UV SAW photodetector is tuned between ∼22% and ∼0.4%.

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