In this article, the field-emission properties of the one-dimensional nanostructure grown on doped silicon substrate have been studied via computer simulation. The classical transport equation is used to describe the carrier transport in the material and solved together with Poisson's equation. The field emission at the emitter-vacuum interface is modeled by the Fowler-Nordheim equation. Our simulation results agree with the experimental results qualitatively. For narrow-band-gap material, the p-type Si substrate will limit the field-emission current in the high applied voltage region. This result can be ascribed to the formation of reverse-biased p-n junction. For wide-band-gap material, however, the p-type Si substrate will enhance the field-emission current, which is attributable to the lower carrier injection barrier height and the stronger driving force offered by the p-type substrate. (c) 2006 American Vacuum Society.