MODEL CALCULATION OF THE FEMTOSECOND CARRIER DYNAMICS IN AL0.48GA0.52AS

We present a model calculation capable of investigating the dynamics of photoexcited carriers in the Al0.48Ga0.52As indirect gap semiconductor. Nearly resonant excitation at the Gamma point produces low excess energy carriers, so that we use Boltzmann like equations and assume thermalized carrier distributions for each of the conduction valleys. Some aspects of the carrier dynamics are discussed and pump and probe measurements are compared to the calculated saturation bleaching, evidencing a very good agreement between theory and experiment. We obtain a value of 3.5 eV/Angstrom A for the D-Gamma X deformation potential.7663749375

INTERVALLEY SCATTERING IN INDIRECT GAP AL0.48GA0.52AS ALLOY

We describe a measurement of the intervalley scattering rate between the GAMMA valley and the subsidiary X and L valleys in a film of Al0.48Ga0.52As alloy. For this concentration of Al the band gap of the alloy is in indirect. We find a time constant for the combined scattering between the GAMMA valley and both the X and L valleys of 120 fs.851195395

Interplay between direct gap renormalization and intervalley scattering in AlxGa1-xAs near the Gamma-X crossover

We report resonant pump and white probe femtosecond spectroscopy in the Al0.42Ga0.58As multivalley semiconductor. For this alloy composition the energy valleys are near the Gamma-X crossover. Our most interesting result refers to the differential transmission below gap which shows carrier induced absorption and a complex dynamics. The data can be modeled if we take into account the dependence of the gap renormalization on the occupation of each conduction band valley. We infer an interplay between direct gap renormalization and the ultrafast redistribution of the photoinjected carriers that follows ultrafast intervalley scattering in the scenario of multiple valleys close in energy in the conduction band. This shows on femtosecond timescale the contribution of the electron exchange interaction to the band gap narrowing in highly excited multivalley semiconductors. (C) 2002 Elsevier Science Ltd. All rights reserved.121418118