Raman scattering in ion-implanted GaN

Raman measurements were performed on molecular beam epitaxially grown GaN before and after implantation with ${\mathrm{Ar}}^{\mathrm{+}},$ ${\mathrm{Mg}}^{\mathrm{+}},$ ${\mathrm{P}}^{\mathrm{+}},$ ${\mathrm{C}}^{\mathrm{+}},$ and ${\mathrm{Ca}}^{\mathrm{+}}$ ions. With increasing ion dose, new Raman peaks arise at 300, 360, 420, and $\text{670\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}},$ independent of the ion species. After rapid thermal annealing at temperatures between 900 and 1150 °C for 15 s, the intensities of the Raman modes decrease with increasing temperature with the exception of the $\text{360\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ mode which shows a maximum in intensity after annealing at 900 °C. The mode at $\text{300\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ is attributed to disorder-activated Raman scattering, whereas the other three modes are assigned to local vibrations of vacancy-related defects.