Undoped zinc oxide (ZnO) and indium-doped (ZnO: In) thin films were grown at different temperatures (250-400 degrees C) on alkali-free borosilicate glass and n-Si (100) substrates by Ultrasonic Spray Pyrolysis method. The structural, compositional, optical and electrical properties of ZnO films were investigated by X-ray diffraction, Scanning Electron Microscopy, Rutherford Back Scattering Spectroscopy, Fourier Transform Infrared spectroscopy, photoluminescence (PL) and the four-point probe technique. The predominance of ultraviolet (UV) and blue emission intensities was found to be closely dependent on the resistivity of the film. The visible emission band (peaking at 432 nm) prevails for low film resistivity, ranging from 10(-2) to 1 Omega.cm. By contrast, for higher resistivity (>1 Omega.cm), there is a predominance of the UV band (382 nm). The PL and photoresponsivity results of fabricated ZnO: In/n-Si(100) heterojunctions prepared at different temperatures are discussed. The maximum spectral response of the ZnO: 8% In/Si heterojunction diode fabricated at 250 degrees C was about 80 mA/W at zero bias. The highlighted results are attractive for the optoelectronic applications. (C) 2015 Elsevier B.V. All rights reserved.