High dose Si- and Mg-implantation in GaN: Electrical and structural analysis

Abstract

The implantation of Si-donors and Mg-acceptors in GaN was studied for doses from 1 × 10 14 to 1 × 10 16 cm −2 and annealing at 1100°C. The transport and luminescence properties were compared to Ar-implanted samples at the same doses. For a Si dose of 1 × 10 16 cm −2 a sheet electron density of 5 × 10 15 cm −2 was measured after annealing. Since a same dose Ar-implant resulted in only a sheet electron density of 3.3 × 10 13 cm −2, the free electron density in the Si-sample is not attributable to implant damage but is the result of electrically active Si-donors. For a Mg dose of 5 × 10 15 cm −2 the sheet carrier concentration is only 8 × 10 11 cm −2 which suggests, even when accounting for the ionization energy of Mg in GaN of ∼ 170 meV, that no significant Mg-activation has occurred or that it is compensated by the implantation induced damage. Channeling Rutherford backscattering and cross-sectional electron microscopy demonstrates that at high doses (6 × 10 15 cm −2) even annealing at 1100°C, as required to activate implanted dopants, does not significantly reduce the implantation induced disorder. Therefore, at least for Si-donors, the complete removal of implant damage is not required to achieve electrically active implanted dopants in GaN.