Mg and Be Ion Implanted GaAs

p‐type layers have been produced in GaAs by implantation of either Mg or Be ions, with the substrate at room temperature, followed by annealing at higher temperatures. The ion source in both cases was a hot‐cathode electron‐bombardment type. The Mg ions were generated by placing metallic Mg in an axial probe inserted into the source, while the Be ions were produced by placing BeCl₂ in the probe. n‐type $\text{〈111〉}$ substrates were implanted with 45‐keV Mg or 40‐keV Be ions, and were subsequently annealed for 15 min at temperatures up to 900°C. The dependence of surface carrier concentration and mobility on ion dose and on postimplantation anneal temperatures was determined using the van der Pauw‐Hall technique.