Facile assembly of SnO2 thin film-based Al/SnO2/Al device for sensing of 260 nm UVC and 365 nm UVA radiation

An Al/SnO2/Al metal-semiconductor-metal (MSM) device was formed by depositing a 55 nm thin film of SnO2 on Si substrate. Structural, surface morphology and optical properties of the SnO2 film were studied. The currentvoltage (I-V) characteristics of the device were recorded under the dark condition followed by 260 nm-UVC and 365 nm-UVA illumination conditions. Under the dark condition, the device shows a resistivity of 8.05 Omega cm at V=1.5 V bias voltage. The device produces nearly symmetric rectifying-type I-V characteristics under forward and reverse bias conditions. The electrical properties of the device were explained using back-to-back Schottky diode model. Under the dark condition, the ideality factor of the junction under forward and reverse bias were estimated to be 1.08 and 1.72 respectively. The external quantum efficiency of the device under UVC was found to be 518.72% and specific detectivity reached as high as 1.03x109 Jones at 2.0 V with a response time of 1 s. The device showed a high signal-to-noise ratio between 0.5 and 1.5 V bias voltages. The values of the ideality factor being greater than 1 was attributed to the presence of point defects in the SnO2 layer as verified by photoluminescence study. This study reveals that the device could be used as a UVC and UVA sensor at a relatively low bias voltage of 1.5 V.