Electrical characteristics of GaN implanted with Si+ at elevated temperatures

Si + implantation at multiple ion energies (30–360keV) 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 5min. At total doses of 2.0×1014cm−2 (corresponding to an approximately uniform Si concentration of ∼4×1018cm−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 (<700Ω∕◻) 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.