Effects of proton implantation on electrical and recombination properties of n-GaN

Effects of implantation with 150 keV protons and 350 keV deuterium ions on deep levels spectra and electrical and recombination properties of n-GaN sa mples were studied for fluences between 8 x 10(13) and 5 x 10(15) cm(-2). I mplantation led to substantial decrease of the electron concentration so th at after the highest dose used, the samples became highly resistive with th e Fermi level pinned near 0.3-0.4 eV from the conduction band edge. We also observed a strong degradation of the minority carriers diffusion length an d a very strong decrease of the band edge luminescence intensity in the hea vily implanted samples. Deep levels spectra measurements showed that proton implantation led to introduction of deep electron traps with activation en ergies near 0.2, 0.3, 0.45, 0.75 and 0.95 eV and of deep hole traps with ac tivation energies of 0.25, 0.6 and 0.9 eV. The results strongly indicate th at among these traps, the 0.75 eV electron traps and/or the 0.6 eV hole tra ps are most likely responsible for the lifetime degradation. Strong recover y of the electric conductivity of the implanted samples was observed starti ng with annealing temperatures near 250 degreesC, whereas no recovery of th e luminescent characteristics could be observed for annealing temperatures as high as 700 degreesC. We compare the results with previously published d ata on proton and He implantation of GaN and discuss possible implications of our findings for practical use in GaN devices isolation. (C) 2000 Elsevi er Science Ltd. All rights reserved.