Dynamical screening and memory effect of non‐equilibrium carrier–carrier scattering in GaAs

Abstract

Given the absence of a Coulomb singularity in the quantum regime, the dependence of dynamical screening in non‐equilibrium carrier–carrier scattering on the dimension of GaAs was examined using the generalized Kadanoff–Baym equation. The screening in a quantum well is stronger than that in the bulk but this has not been previously understood. This dependence also applies to the Fröhlich interaction because, in momentum space, the electric flux density of small‐angle scattering is stronger in a lower dimension. Calculations also revealed the memory effect; based on these, the quantum kinetic oscillation was conceptualized. As time evolves, the scattering rate increases at the early stage and causes hole burning in the carrier's distribution. This effect enables the dependence of the average relaxation time on the carrier density to become independent of the sample's dimension, unlike in the Boltzmann regime. This work can eliminate the apparent contradiction between Shank's and Haug's experimental results. Finally, an experimental problem regarding the anomalously fast thermalization of non‐equilibrium carriers immersed in cold electrons in a quantum well was investigated and a reasonable explanation is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)