The authors report enhanced ultraviolet electroluminescence at room temperature from a diode structure consisting of vertically oriented ZnO nanorod arrays grown on a p-typed silicon substrate. Excitonic emitting peak at wavelength of 385 nm with a full width at half maximum (FWHM) of 23 nm and a defect-related visible emitting peak at the wavelength of 546 nm with a FWHM of 124 nm are observed from this structure under forward-bias voltage. The intensity ratio of the ultraviolet peak and the visible peak reaches 4.7. The scanning electron microscope, x-ray diffraction, energy dispersive x ray, I-V, and electroluminescence measurements demonstrate that good crystal structure and rectifying diodelike behavior are obtained and defect-related visible light emission is greatly restrained. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3079657]