ZnO nanorod arrays on a transparent indium tin oxide/glass substrate were synthesized using a hydrothermal method. The tip diameters of the fabricated ZnO nanorods varied between 20 and 30 nm with lengths of 1 μm. Addition of Al3+ ions to the reaction solution produced Al-doped ZnO nanorods. The morphology and crystallinity of Al-doped ZnO nanorods were investigated by scanning electron microscopy and transmission electron microscopy. The crystal structure was analyzed by X-ray diffraction spectroscopy. Inductively coupled plasma atomic emission spectroscopy confirmed the level of Al doping. The electrical properties were obtained using I- V data from an entire structure of ZnO nanorod arrays.