An ion source apparatus for ion implantation is described, including an ion source chamber, and a consumable structure in or associated with the ion source chamber, in which the consumable structure includes a solid dopant source material susceptible to reaction with a reactive gas for release of dopant in gaseous form to the ion source chamber, wherein the solid dopant source material comprises gallium nitride, gallium oxide, either of which may be isotopically enriched with respect to a gallium isotope, or combinations thereof.