We fabricate MgyZn1-yO metal-semiconductor-metal ultraviolet photodetectors by integrating Au electrodes (with different electrode spacings) onto a semiconductor film (Mg0.20Zn0.80O or Mg0.42Zn0.58O), prepared by the radio frequency magnetron sputtering deposition method. As expected, the Mg0.20Zn0.80O photodetectors have a larger responsivity than the Mg0.42Zn0.58O ones when the electrode spacing and bias voltage are constant. More interestingly, the responsivity of all the MgyZn1-yO photodetectors increase with decreasing electrode spacing for the same bias. These results are well-understood in terms of the role played by the metal-semiconductor junction. (C) 2016 Elsevier Ltd. All rights reserved.