The design and operation of a compact single‐grid, ultrahigh‐vacuum‐compatible, low‐energy ion gun capable of utilizing gaseous, liquid, or solid source material are described. The gun can provide>100 μA/cm2at ion energies ranging from 20 to 500 eV, and grid and filament lifetimes of several hundred hours have been obtained while operating with Zn and As. Current–voltage characteristics of the source as well as resulting ion beam profiles are reported. With appropriate grid design, uniform ion beam intensities were obtained over 4 cm diam wafers at a distance of 20 cm from a 1 cm diam ion source. In initial experiments using the ion source for accelerated‐ion doping of (100)Si and (100)GaAs, several orders of magnitude increases in elemental As and Zn incorporation probabilities were observed.