Al/ZnO/p-Si, Al/PMMA/p-Si and Al/PMMA/ZnO/p-Si structures were fabricated. Based on the measured current voltage (C-V) and capacitance voltage curves, the electrical characteristics of these heterostructures such as ideality factor, barrier height and series resistance of each structure were analyzed and then compared with those of Al/PMMA/ZnO/p-Si. According to C-V measurement, it was found that the Al/PMMA/ZnO/p-Si structure indicates the better electronic performance rather than other structures. The obtained results represent low series resistance (19.3 Omega) after coating with polymethyl methacrylate (PMMA) over ZnO/p-Si heterojunction structure for Al/PMMA/ZnO/p-Si heterostructure. (C) 2015 Elsevier Ltd. All rights reserved.