Resonant two-phonon Raman scattering in GaAs: A sensitive probe for implantation damage and annealing

We have used resonant Raman scattering by two longitudinal optical (LO) phonons in GaAs to probe ion implantation induced damage and its annealing. It was found that the strength of the two-LO phonon peak is very sensitive to ion bombardment induced damage as demonstrated by the change in the Raman spectrum after sputtering with low-energy Ar ions. For the study of ion implanted and thermally annealed material the two-LO phonon scattering is more sensitive to the lattice perfection than the first-order Raman spectrum especially in the region where electrical activation of the dopant sets in. Spatially resolved Raman spectroscopy revealed considerable variations of the crystalline perfection across the annealed sample. The latter study was particularly facilitated by using optical multichannel detection.