In this work we report the structural and optical properties of ion implanted GaN. Potential acceptors such as Ca and Er were used as dopants. Ion implantation was carried out with the substrate at room temperature and 550 deg C, respectively. The lattice site location of the dopants was studied by Rutherford backscattering/channeling combined with particle induced X-ray emission. Angular scans along both [0001] and [101-bar1] directions show that 50 percent of the Er ions implanted at 550 deg C occupy substitutional or near substitutional Ga sites after annealing. For Ca we found only a fraction of 30 percent located in displaced Ga sites along the [0001] direction. The optical properties of the ion implanted GaN films have been studied by photoluminescence measurements. Er-related luminescence near 1.54 mu m is observed under below band gap excitation at liquid helium temperature. The spectra of the annealed samples consist of multilane structures with the sharpest lines found in GaN until now. The green and red emissions were also observed in the Er doped samples after annealing.
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