Gallium-doped n-type CdS nanowires (NWs) were successfully synthesized via a thermal evaporation method. The conductivities of the CdS NWs were dramatically improved by nearly nine orders of magnitude after Ga doping, and could be further tuned over a wide range by adjusting the doping level. High-performance metal-insulator-semiconductor field-effect transistors (MISFETs) were constructed based on the single CdS : Ga NW with high-κ Si(3)N(4) dielectrics and top-gate geometries. In contrast to back-gate FETs, the MISFETs revealed a substantial improvement in device performance. Nano-light emitting diodes (nanoLEDs) were fabricated from the CdS : Ga NWs by using a n-NW/p(+)-Si substrate hybrid device structure. The nanoLEDs showed a bright yellow emission at a low forward bias. It is expected that the Ga-doped CdS NWs with controlled electrical transport properties will have important applications in nano-optoelectronic devices.