Herein, the influence of crystallographic polarity on the properties of ZnO polycrystalline thin films deposited by magnetron sputtering, has been studied. The electrical and optical properties of undoped ZnO and heavily Ga-doped ZnO thin films showed significant differences between Zn polarity and O polarity. The Hall mobility and carrier concentration of the undoped ZnO thin films with Zn polarity were higher than those with O polarity. The ZnO film with Zn polarity showed a dominant near-band-edge emission, while that with O polarity showed relatively intense deep-level emission in the visible wavelength region. It was suggested that acceptor-type defects tend to be formed in the ZnO films with O polarity. The Ga-doped ZnO films deposited on the Zn-polar ZnO layer showed a higher carrier concentration and Hall mobility as compared to deposition on O-polar ZnO. Crystallographic polarity is thus a very important factor for controlling the properties of polycrystalline ZnO-based thin films deposited on glass substrates. (C) 2018 Elsevier B.V. All rights reserved.