Study of coherent LO phonon-plasmon coupled modes in n-GaAs by spectrally resolved pump-probe measurement

摘要

The coherent LO phonon-plasmon coupled modes (LOPC modes) in n-GaAs have been studied by using a spectrally resolved pump-probe measurement which is performed by detecting probe beams after passing through a bandpass filter with a bandwidth of 10 em. As the detection wavelength of the probe pulse comes closer to the band edge (approx 870 em), the intensity of the lower branch of the LOPC mode (L_- mode) is increased and the decay time becomes longer. The wavelength dependence of the intensity will result from the resonance effect of the probe light. The wavelength dependence of the decay time indicates that the decay of the L_- mode will be related to the intraband relaxation of the photoexcited carriers coupled with LO phonon due to the electron-hole scattering in the presence of the plasmon.