Self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques. The NRs are uniformly grown on 2-inch wafer along  direction. Single-crystalline wurtzite structure of ZnO NRs was confirmed by X-ray diffraction. The average diameter, height, and density of NRs are found 48 nm, 750 nm, and 1.26 × 1010 cm-2, respectively. The current-voltages (I-V) characteristics of ZnO NRs/Si heterojunction (HJ) were studied in the temperature range of 120-300 K and it shows a rectifying behavior. Barrier height (φB) and ideality factor (η) were estimated from thermionic emission model and found to be highly temperature dependent in nature. Richardson constant (A*) was evaluated using Richardson plot of ln(Io/T2) versus q/kT plot by linear fitting in two temperature range 120-180 K and 210-300 K. Large deviation in Richardson constant from its theoretical value of n-Si indicates the presence of barrier inhomogeneities at HJ. Double Gaussian distribution of barrier height with thermionic equation gives mean barrier heights of 0.55 ± 0.01 eV and 0.86 ± 0.02 eV for two different temperature regions 120-180 K and 210-300 K, respectively. Modified Richardson plot provided two values of Richardson constant for two temperature regions. However, for higher temperature range (210-300 K), the calculated value of Richardson constant ∼123 A cm-2 K-2 was close to the ideal Richardson constant for n-Si. © 2014 AIP Publishing LLC.