Daniel W. Bailey

Monte Carlo modeling of femtosecond relaxation processes in AlGaAs/GaAs quantum wells

Results are presented from Monte Carlo simulations of the femtosecond relaxation of photoexcited electrons in AlGaAs/GaAs quantum wells. Two experiments are simulated: in one electrons are initially excited at high energies far from equilibrium, and in other electrons are excited at low energies close to the bottom of the band. The effects of electron-electron, polar optical phonon, and intervalley deformation potential scattering are studied. For comparison, subpicosecond relaxation in bulk GaAs is also discussed. >

Ensemble Monte Carlo simulations of femtosecond energy relaxation of photoexcited electrons in bulk GaAs

Abstract We present results of ensemble Monte Carlo simulations of the femtosecond relaxation of photoexcited electrons in bulk GaAs. Our results are in qualitative agreement with the experimental data of Rosker, Wise and Tang (1986) and show that the fast relaxation component (∼34 fs) is primarily due to Γ→L scattering with a minor contribution from electron-electron scattering. The intermediate relaxation component (∼160 fs) is a result of the energy loss of electrons in the Γ valley which occurs chiefly by polar optical phonon (POP) scattering.

Ensemble Monte Carlo simulations of femtosecond thermalization of low‐energy photoexcited electrons in GaAs quantum wells

We present results of ensemble Monte Carlo simulations of the room‐temperature relaxation of nonthermal photoexcited electrons in GaAs quantum‐well structures. Electrons are excited at a mean energy of 20 meV above the band edge, similar to the experiments of Knox et al. [Phys. Rev. Lett. 56, 1191 (1986)] and Oudar et al. [Phys. Rev. Lett. 55, 2075 (1985)]. Since this energy is less than the optical‐phonon emission threshold, energy relaxation occurs primarily via carrier‐carrier scatterings. We find that the excited electrons thermalize with the background electrons within 200 fs, in agreement with experiment.

Femtosecond studies of intervalley scattering in GaAs and AlxGa1-xAs

Abstract Results are presented from ensemble Monte Carlo simulations of the relaxation of photoexcited electrons and holes. The results are compared directly with three types of femtosecond optical experiments: transient absorption saturation, pump and continuum probe, and tunable pump-probe experiments. For these experiments we find that intervalley scattering has a dominant effect for the first several hundred femtoseconds, and that electron-electron scattering is only important at later times.

Intersubband dynamics in modulation doped quantum wells

Abstract A theoretical investigation of the dynamics of intersubband transitions in modulation doped multiple narrow GaAs / Al x Ga 1− x As quantum well structures by emission of GaAs (well) and Al x Ga 1− x As (barrier) slab and interface mode polar optical phonons is presented. Photo-excited carrier behavior is interpreted via Monte Carlo simulations which predict long time constants for electron relaxation.

Monte Carlo Simulations Of Femtosecond Spectroscopy In Semiconductors

Simulations of electron dynamics in semiconductors during the first half picosecond after optical excitation by a 2-eV laser are reported. Emphasis is given to a comparison between the effects of intervalley phonon scattering, electron-electron scattering and electron-polar optical phonon interactions. The advantages of Monte Carlo simulations for the visualization of the complex processes is stressed.