Rutherford backscattering study on high dose Mg-ion implanted GaN bulk single crystal

Lattice displacements before and after annealing for the high dose Mg-ion implanted GaN with 5.0 x 10^15 cm^-2 and 1.0 x 10^16 cm^-2 are evaluated by Rutherford backscattering spectroscopy (RBS) using 1.5-MeV H^+ ions. The Mg-ion implantation into GaN bulk single crystal is performed at room temperature with implantation energy of 150 keV. Annealing is performed at 1230℃ for 1 min in a nitrogen atmosphere. Although the gallium displacement for the dose of 5.0 x 10^15 cm^-2 is observed, the surface of GaN for the dose of 1.0 x 10^16 cm^-2 shows the polycrystalline-like feature. The high dose Mg-ion implanted GaN such as 1.0 x 10^16 cm^-2 remains the lattice displacement in the implanted layer under the present annealing condition. From photoluminescence measurements, the band edge emission for un-implanted GaN is observed at 358 nm (3.46 eV), but this emission is not observed for as-implanted GaN and annealed ones. The disappearance of the band edge emission is considered to be due to the collapse of the crystal structure of the GaN surface due to the Mg-ion implantation.