Vertically aligned zinc oxide (ZnO) nanorods (NRs) were grown on the ion-plated Ga-doped ZnO (GZO) seed layers by chemical bath deposition from the mixed aqueous solutions of zinc nitrate hexahydrate and hexamethylenetetramine using the deionized water with a low resistivity or that with a high resistivity. The difference in the resistivity of the deionized water resulted in the differences in both the growth rates along the length- and width-directions and the different growth time dependences of the morphological, residual stress and photoluminescence properties of the NRs. The dark current-voltage curves of poly(3,4-ethylenedioxythiophene)poly (styrenesulfonate) (PEDOT: PSS)/ZnO NRs/GZO heterostructures showed rectifying characteristics, suggesting the formation of Schottky junctions. It was found that the barrier height of the Schottky junction decreases with the increase in the growth time of the ZnO NRs layer. Moreover, the PEDOT:PSS/ZnO NRs/GZO heterostructures exhibited the photocurrent, which is effectively generated under the illumination of 360 nm UV light. The rise and decay times of the photocurrent were typically several seconds and several hundreds seconds, respectively. The observed photoconductive mechanism cannot be explained without the help of the change in the Schottky barrier height due to the adsorption and desorption of the oxygen molecules at the surface of the NRs.