ZnO:Ca MSM ultraviolet photodetectors

Photoresponse of calcium doped zinc oxide (ZnO:Ca) metal-semiconductor-metal (MSM) UV detectors are reported. Photosensitive ZnO:Ca films exhibit high transparency in the visible region, show polycrystalline, hexagonal wurtzite structure, having c-axis preferred growth. Noticed redshift of 60 meV in the optical band gap for ZnO:Ca (3 wt%) thin film is attributed to increased crystallite size. Improved n-type conductivity in ZnO with Ca doping is due to increased carrier concentration, MSM photodetector fabricated with, 3 wt% Ca doped ZnO exhibit higher responsivity of 3.05A/W at 365 nm UV illumination. Transient response measurements show reasonably fast switching with a rise and fall time of 15s and 26s respectively. The obtained results suggest, ZnO:Ca can be used as active material in the fabrication of UV photodetectors.