Resonant Raman scattering on free and bound excitons in GaN - art. no. 165314

We comprehensively investigated the resonant Raman scattering effect in GaN at low temperatures applying a frequency-doubled titan-sapphire laser as q uasicontinuous excitations source. The scattering cross sections of the E-2 (high), A(1)(LO), and 2A(1)(LO) phonon modes exhibit a resonance enhancemen t at the donor- and acceptor-bound excitons. The enhancement of the A(1) (L O) modes is even stronger than for the nonpolar E-2(high) mode due to a Fro hlich interaction. Furthermore, the temporal behavior of the phonons near t he resonance was studied using time-resolved spectroscopy. We found that th e resonance process below the bound excitons is likely to proceed via the f ree exciton as intermediate state.