Hot-wire chemical vapour deposition (CVD) was applied to grow zinc oxide (ZnO)-based transparent conducting oxide films. Indium (In)-, gallium (Ga)-, and aluminium (Al)-doped ZnO films were deposited at 400 degrees C on sapphire-R, Si (100) and glass substrates using a cold wall pulsed liquid injection CVD system containing nichrome wires installed in front of the substrate holder. Zn, In, Al 2,2,6,6-tetramethyl-3,5-heptanedionates, and Ga 3,5-pentanedionate dissolved in 1,2-dimethoxyethane were used as precursors. Hall measurements were performed to evaluate the resistivity, carrier concentration, and carrier mobility in doped ZnO films grown on sapphire substrates at wire currents of 6 A and 9 A. The influence of the dopant type, doping level, substrate, and wire heating current on crystallinity and the electrical and optical properties of the films was investigated and discussed. The best electrical properties were obtained for Al- and Ga-doped films grown at 9 A wire current (resistivity approximate to 1 x 10(-3) Omega cm, carrier mobility approximate to 50 cm(2) V-1 s(-1) and carrier concentration approximate to 1 x 10(20) cm(-3)). The films exhibited a high transmittance in the mid-infrared region (approximate to 90% at 2.5 mu m). Additional annealing of the films at 400 degrees C in a mixture of Ar and hydrogen (10%) resulted in the increase in carrier concentration and mobility and in the reduction of film resistivity. (C) 2015 Elsevier B.V. All rights reserved.