Electron-hole scattering in GaAs quantum wells.

Abstract

Momentum and energy relaxation of minority carriers in GaAs quantum wells is studied in a series of experiments. At low temperatures electron-hole scattering is the dominant scattering mechanism for minority carriers in high-quality samples, causing dramatic carrier-drag effects (e.g., negative drift or negative absolute mobility) in the minority-carrier transport. Quantitative analysis of all-optical drift-velocity measurements shows that the momentum relaxation times of minority electrons in a hole plasma are much shorter (40--100 fs) than those of minority holes in an electron plasma (2--5 ps). Besides the different effective masses, part of this large difference is due to degeneracy of the electron plasma and due to effects from two dimensionality. At high electric fields, energy transfer between electrons and holes in the nonequilibrium plasma is studied. Characteristic transfer times of 200--500 fs (temperature dependent) are determined from simultaneous measurements of minority-electron energy-loss and energy distribution.