The fabrication of Al-doped ZnO films by an aqueous solution process using a continuous circulation reactor was studied. By heating ZnO-saturated ammonia solutions containing 2-10 mM Al(NO3)(3) with pH 10.7 at 90 degrees C under ambient pressure, polycrystalline ZnO films with Al content of 1-2 at.% were deposited. The carrier concentration of ZnO films increased with increasing Al content, indicating that Al was successfully incorporated into the ZnO crystals. The Al-doped ZnO films had carrier concentrations of 10(19)-10(20) cm(-3) and mobilities of 0.7-7 cm(2)/V/s after annealing at 300 degrees C in air. (c) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim