Defect induced raman transition in non-stoichiometric Ga-rich GaAs - a pseudolocalized vibrational mode of the GaAs antisite?

Raman scattering with below band gap excitation has been used to study as grown GaAs pulled from Ga-rich melts. A vibrational pseudolocalized defect mode is observed at 225 cm E-1 in material, which also contains the 78/203 meV double acceptor. The temperature variation of the 225 cm E-1 Raman peak is found to depend on the charge state of the double acceptor. These findings indicate that the 78/203 meV acceptor levels and the 225 cm E-1 vibrational mode may arise from the same defect center. Possible models for this center are discussed including the Ga-antisite defect. (IAF