A high-quality ZnO nanorod array (NRA) has been successfully grown on a Si wafer by a wet-chemical process, where the Si wafer was dip-coated with 4 nm sized ZnO nanoparticles as a buffer and seed layer prior to the crystal growth. It is found that the as-prepared ZnO NRA has a threshold power density of similar to 70 kW cm(-2), which is comparable to the lowest one determined for ZnO NRAs on Al2O3 substrates (40 kWcm(-2)). The ultraviolet lasing efficiency of the ZnO NRAs is thus similar for both substrates.