Raman scattering studies on low-energy nitrogen-implanted semi-insulating GaAs

Liquid-encapsulated Czochralski (LEC) grown undoped semi-insulating (SI) ga llium arsenide (GaAs) single crystals have been implanted with 120 keV nitr ogen ion (N+) of fluences 1 x 10(14), 1 x 10(15) and 1 x 10(16) cm(-2) Rama n scattering studies of the as-grown and implanted samples have been carrie d out at room temperature and analyzed. It is observed that the AI(LO) phon on mode frequency decreases with increase of fluence, whereas the full widt h at half maximum (FWHM) increases and the area under the peak decreases. A ll these effects are due to the lattice disorder induced by the implantatio n. The implanted samples have been annealed at 673 K. They show a partial r ecovery of the AI(LO) phonon mode frequency and the FWHM which tend towards the unimplanted values due to partial annealing of the implantation-induce d lattice damage. Tile post-implantation annealed samples show an increase of the area under the peak due to the enhanced Raman scattering caused by t he surface roughness which was caused by the implantation. This increase in area was less at high fluences because of the residual lattice damage indu ced by the implantation, which caused the decrease of the area. (C) 2001 El sevier Science B.V. All rights reserved.