Reduced graphene oxide (rGO)/ZnO heterostructure was prepared via electrochemical deposition directly on Hummers method derived rGO membranes and the corresponding diodes had been fabricated. Rectifying I-V curve was obtained by modifying the functional groups on the surface of rGO. Further investigation for GO based transistors showed that the conductivity of rGO could vary from n-type to p-type under different annealing conditions. Based on Lerf-Klinowski model and X-Ray photoelectron spectroscopy, it was found that the C-sp(2), hydroxyl and epoxy in rGO would be responsible for the change of electrical properties. It was also concluded that reasonable p-type conductivity of rGO for obtaining rectifying rGO/ZnO heterostructure occurred while the percentage of C-sp(2) content was about 54% with the C-sp(2)/(OH+C-O-C) ratio around 1.6. (C) 2016 Elsevier Ltd. All rights reserved.