Si+ implantation at multiple ion energies (30–360 keV) into GaN for n-type doping was carried out at substrate temperatures from 27 to 700 °C, followed by annealing at 1150–1400 °C for 5 min. At total doses of 2.0×1014 cm−2 (corresponding to an approximately uniform Si concentration of ∼ 4×1018 cm−3), the use of elevated implant temperature does not produce improved electrical characteristics. For anneal temperatures below ∼ 1300 °C, the resulting sheet resistance of the GaN implanted at 700 °C was approximately a factor of 2 higher than for room-temperature implantation, mainly through a lower sheet carrier density. At the higher annealing temperatures (>1300 °C), elevated implant temperature produced similar sheet resistances to implantation carried out at room temperature. For annealing at 1300 °C, the lowest sheet resistances (<700 Ω/◻) and highest activation efficiencies ( ∼ 65%) were obtained for implant temperatures <400 °C. The most plausible explanation is that at these doses, SiGa (i.e., donor state) site occupation is not a strong function of the initial amount of damage created by the implantation.