- Conference date: 30 April–3 May 2012
- Location: New Mexico, USA
Theoretical modeling of photo-induced electron-hole plasma and bandgap dynamics in GaAs at high femtosecond laser intensities (∼ TW/cm2) employing a quantum kinetic formalism based on a generalized Boltzmann-type equation, predicts for the first time, against expectations, saturation of plasma densities despite of the strong direct bandgap narrowing. Though the transient electronic bandgap renormalization provides a significant positive feedback for all relevant - single-photon and impact - ionization mechanisms, which is clearly observable at moderate (sub-TW/cm2) laser intensities, the counterintuitive plasma density saturation at higher laser intensities and high plasma densities (∼ 1022 cm−3) is dictated by much stronger negative feedback, originating from a highly-nonlinear transient enhancement of the corresponding Auger recombination coefficient for the shrinking bandgap. These theoretical predictions are in semi-quantitative agreement with results of previous time-resolved reflectivity experiments, which support this newly predicted process, self-limiting ionization dynamics in strongly photo-excited semiconductors, such as GaAs, with induced band-gap shrinkage.
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