Ultrafast dephasing of continuum transitions in bulk semiconductors

1999/06/15 by S. Arlt, U. Siegner, J. Kunde +2 · 1 citation
Physics and Astronomy · #Quantum and electron transport phenomena #Semiconductor Quantum Structures and Devices #Spectroscopy and Quantum Chemical Studies

paper · doi:10.1103/physrevb.59.14860

openalex publication_date 1999/06/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/26

Abstract

We have studied the coherent emission from bulk semiconductors by spectrally resolved and spectrally integrated four-wave mixing (FWM) with broadband 16-fs pulses in the carrier density range from 1\ifmmode×\else\texttimes\fi10¹⁶cm^\mathrm\ensuremath-3 to 6\ifmmode×\else\texttimes\fi10¹⁷cm^\mathrm\ensuremath-3. In GaAs, only continuum transitions are excited, while both excitonic and continuum transitions are excited in Al_0.06Ga_0.94As. The decay of the FWM signal for positive time delays unambiguously reflects the dephasing of the continuum, irrespective of the excitation of excitonic transitions. We find identical ultrafast sub-20-fs decay times of the coherent emission from continuum transitions in GaAs and Al_0.06Ga_0.94As, independent of the excess excitation energy. These decay times depend only weakly on the carrier density for densities below 10¹⁷cm^\mathrm\ensuremath-3. The continuum dephasing is analyzed considering carrier-carrier and carrier-LO-phonon scattering in a relaxation rate approach. The excitonic transitions in Al_0.06Ga_0.94As dominate the FWM signal at negative time delays.

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