Outgoing multiphonon resonant raman scattering and luminescence in Be- and C-implanted GaN

We have performed outgoing resonant Raman scattering and photoluminescence measurements on as-grown, Be- and C-implanted GaN in the temperature range of 77-330 K. In implanted GaN after postimplantation annealing at 1100 degreesC, the A(1)(LO) multiphonons up to the seventh order were observed with the very strong four longitudinal optical (LO) and five LO modes at similar to2955 and similar to3690 cm-1, respectively, showing extraordinary resonance behavior. With the sample temperature, these two modes significantly decreased and increased in intensity, respectively. The phenomenon is attributed to the variation of resonant conditions due to the shift of the band gap energy. Meanwhile, the combination of E-2(high) and quasi-LO phonons was strongly enhanced by quasi-LO phonon involvement and thus the corresponding overtones can be clearly observed even up to the sixth order (m=6). The mechanisms that such strong outgoing multiphonon resonance Raman scattering occurred to implanted GaN instead of high-quality as-grown GaN samples can be attributed to the strong Frohlich-induced scattering by LO phonons and exciton-mediated resonant Raman scattering with impurity inducement. (C) 2002 American Institute of Physics.