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Functionalizing self-assembled GaN quantum dot superlattices by Eu-implantation
Magalhães, S.; Peres, M.; Fellmann, V.; Daudin, B.; Neves, A.J.; Alves, E.; Monteiro, T.; Lorenz, K.Self-assembled GaN quantum dots (QDs) stacked in superlattices (SL) with AlN spacer layers were implanted with Europium ions to fluences of 1013, 1014, and 1015 cm−2. The damage level introduced in the QDs by the implantation stays well below that of thick GaN epilayers. For the lowest fluence, the structural properties remain unchanged after implantation and annealing while for higher fluences the implantation...
Optical doping and damage formation in AIN by Eu implantation
Lorenz, K.; Alves, E.; Gloux, F.; Ruterana, P.; Peres, M.; Neves, A. J.; Monteiro, T.AlN films grown on sapphire were implanted with 300 keV Eu ions to fluences from 3×1014 to 1.4×1017 atoms/cm2 in two different geometries: “channeled” along the c-axis and “random” with a 10° angle between the ion beam and the surface normal. A detailed study of implantation damage accumulation is presented. Strong ion channeling effects are observed leading to significantly decreased damage levels for the chan...
Up conversion from visible to ultraviolet in bulk ZnO implanted with Tm ions
Monteiro, T.; Neves, A. J.; Soares, M. J.; Carmo, M. C.; Peres, M.; Alves, E.; Rita, E.We report on the up-converted ultraviolet near-band edge emission of bulk ZnO generated by visible and ultraviolet photons with energies below the band gap. This up-converted photoluminescence was observed in samples intentionally doped with Tm ions, suggesting that the energy levels introduced by the rare earth ion in the ZnO band gap are responsible for this process. ; FCT/FEDER - POCTI/CTM/45236/02 ; FCT/F...
Near-band-edge slow luminescence in nominally undoped bulk ZnO
Monteiro, T.; Neves, A.J.; Carmo, M.C.; Soares, M.J.; Peres, M.; Wang, J.; Alves, E.; Rita, E.; Wahl, U.We report the observation of slow emission bands overlapped with the near-band-edge steady-state luminescence of nominally undoped ZnO crystals. At low temperatures the time-resolved spectra are dominated by the emission of several high-energy bound exciton lines and the two-electron satellite spectral region. Furthermore, two donor-acceptor pair transitions at 3.22 and 3.238 eV are clearly identified in temper...
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