Carrier capture into InAs/GaAs quantum dots via multiple optical phonon emission

We have performed nondegenerate optical pump-probe experiments with subpicosecond laser pulses to investigate the dynamics of carrier capture into self-assembled InAs/GaAs quantum dots. For low excitation intensities the capture rate depends only slightly on excitation density, whereas a clear dependence on crystal temperature is observed. This temperature dependence can be explained by assuming that the emission of four longitudinal optical (LO) phonons and one longitudinal acoustic phonon is the dominant capture process for electrons. This assumption is consistent with the finding that, for electrons in the conduction band, the energetic separation between the single quantized quantum dot state and the onset of the two-dimensional states of the InAs wetting layer is slightly more than the energy of four LO phonons. (C) 2001 American Institute of Physics.