Resonant Raman scattering near the donor-acceptor transition in GaAs

Resonant enhancement of LO and TO phonon Raman scattering is observed in GaAs when the energy of the exciting light h(cross) omega p coincides with a donor-to-acceptor transition. Strong additional Raman satellites arise on the high-energy side of the resonance curve (1.495<h(cross) omega p<1.510 eV). These satellites are ascribed to localized phonons associated with specific donor-acceptor pairs. This interpretation is substantiated by the observation that their Raman shifts increase with decreasing donor-acceptor separation R, according to Delta E varies as exp(-2R/aD).