ZnO based Back- and Front-Illuminated Photoresistor for UV Sensing Applications

This work presents a versatile and low-cost photoresistor based on zinc oxide (ZnO). ZnO thin films were grown by RF reactive magnetron sputtering technique onto fused silica substrates. Metal planar electrodes were fabricated on top of the films to obtain a photoresistor. A device was tested for UV power amounts up to 65 mW/cm
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at 365 nm. The UV sensing performances were investigated for UV light illumination from the top surface of the ZnO film or from the bottom side through the substrate. Preliminary results highlight a dark current of 75 pA/cm
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at 1 V bias and electro-optical responsivities of around 1.1 μA/W and 540 nA/W for front-illumination and back-illumination mode, respectively. These data, together with the capability of the sensor to adapt to different scenarios, encourage possible implementations in the field of UV sensing in harsh environments.