Optical properties of As-grown, alpha-particle irradiated and N-2(+)-ion implaned GaN

We report an investigation of the optical response of unintentionally doped GaN on sapphire submitted to alpha particle irradiation and N-2(+)-ion imp lantation at 5 keV. Probing the resulting damage by Raman spectroscopy we f ind that, upon implantation, the ratio of A(1)(LO) and E-2 modes increases. This shows that some free-carrier activation accompanies the implantation damages. Probing next the change in optical response by low temperature pho toluminescence, we demonstrate a complex behavior of the near-band-edge (NB E) excitonic lines which is discussed in terms of implantation-induced effe cts.