Ensemble monte carlo study of nonequilibrium carrier dynamics in photo-excited p-i-n, structures

Light scattering from conduction electrons (or from valence holes) can give information on the time-resolved velocity distribution of nonequilibrium carriers. The experimental approach utilizes, e.g., Raman scattering from the single particles to ascertain the velocity distribution. Calculation of the distribution function through an ensemble Monte Carlo technique allows a comparison between the experiment and theory. Here, this is demonstrated with studies of a GaAs p-i-n structure embedded within cladding AlAs layers. The calculations are compared with experimental results that have recently been published on the same structure. For time scales of several hundred femtoseconds, the hot carrier transport that is probed by the single-particle Raman scattering is dominated by the transport in the Gamma valley, and overshoot velocities 4-5 x 10(5) cm/sec are observed

ENSEMBLE MONTE-CARLO SIMULATION OF RAMAN-SCATTERING IN GAAS

A picosecond laser excited GaAs p-i-n structure is studied using an ensemble Monte Carlo method to determine the temporal and spatial evolution of the hot electron distribution function. The experimental set-up we simulate is a novel method based on Raman scattering of light from the electrons to measure the drift velocity of electrons in GaAs at high electric fields. It is observed that the simulation agrees with the experimental results, however, the measured velocity is actually averaged over the time evolution of the spatial distribution of the Raman probe in the sample and underestimates the average velocity of electrons over the pulselength excited in the (Gamma) conduction band of a 1.909 eV laser pulse, which is calculated to be in the order of 8.5 X 107 cm/sec for fields of 25 kV/cm at a temperature of 77 K