Fabrication and characterization of Al:ZnO based MSM ultraviolet photodetectors

• Al doped ZnO thin films were deposited on Si substrates by RF sputtering.
• The structural properties of AZO thin films were investigated by XRD and SEM.
• AZO thin films based MSM UV photodetectors were fabricated.
• Palladium was used as metal electrodes.
• The effect of inter-electrode spacing on photo current of detectors was studied.

This work reports fabrication and characterization of aluminum doped zinc oxide (AZO) thin films based metal–semiconductor–metal (MSM) ultraviolet photodetectors. AZO thin films were grown on Si substrates at room temperature by radio-frequency magnetron sputtering method. Four interdigited metal–semiconductor–metal (MSM) devices with equal inter-electrode spacing and width of 5 μm, 10 μm, 20 μm and 50 μm were fabricated by lithography. Palladium was used as metal electrodes and ultraviolet (UV) light of wavelength 372 nm and power 2.8 μW is used as a UV source. The variation in the value of dark current and photo current according to inter electrode spacing were examined for all the four MSM photodetectors. It was seen that in both conditions (under dark as well as under UV illumination), the current decreases as the spacing between electrodes increases. The results show that the effect of inter-electrode spacing on the dark current is more significant than that of photo current. These investigations will be useful for designing high-performance optoelectronic devices based on AZO thin films.