$n\text{-}\mathrm{Zn}\mathrm{O}∕\mathrm{Si}{\mathrm{O}}_x∕n\text{-}\mathrm{Si}$ and $n\text{-}\mathrm{Zn}\mathrm{O}∕\mathrm{Si}{\mathrm{O}}_x∕p\text{-}\mathrm{Si}$ heterostructured light-emitting diodes have been fabricated using metal-organic chemical-vapor deposition for a comparison study. $n\text{-}\mathrm{Zn}\mathrm{O}∕\mathrm{Si}{\mathrm{O}}_x∕p\text{-}\mathrm{Si}$ heterostructures show diodelike rectifying current-voltage characteristic with low breakdown voltage, while $n\text{-}\mathrm{Zn}\mathrm{O}∕\mathrm{Si}{\mathrm{O}}_x∕n\text{-}\mathrm{Si}$ heterostructures show symmetric nonlinear current-voltage behavior due to the double Schottky barriers at the interface. Both types of diodes emit light when a positive bias applied at Si side. Ultraviolet emission at $\sim 390\mathrm{nm}$ with an orange-emission centered at $\sim 600\mathrm{nm}$ were observed in electroluminescence spectra of $n\text{-}\mathrm{Zn}\mathrm{O}∕\mathrm{Si}{\mathrm{O}}_x∕n\text{-}\mathrm{Si}$ diodes, while whitish emission centered at $\sim 520\mathrm{nm}$ was observed for $n\text{-}\mathrm{Zn}\mathrm{O}∕\mathrm{Si}{\mathrm{O}}_x∕p\text{-}\mathrm{Si}$ diodes. The emission mechanisms were discussed.