Thin films of undoped and Ga-doped ZnO with different doping concentrations (0, 3, 5, 7 wt.%) were deposited on (100) silicon substrates by RF magnetron sputtering using a powder target. The results show that the devices have good rectifying behaviors with an ideality factor values in the range of 1.16-1.81 and a barrier height values in the range of 0.60-0.64 eV based on the IÂV characteristics. Also, CheungÂs functions were used to estimate the series resistance of the diode. Fromthe CÂV characteristics, it is shown that the capacitance increases with decreasing frequencies. CÂ V measurements give higher barrier than those obtained fromIÂVmeasurements. The results demonstrate that the structural and electrical properties of ZnO/p-Si heterojunction diodes are controlled by the Ga dopant content.