Saturated electron drift velocity at high electric fields in AlGaAs/GaAs/AlGaAs heterostructures

Abstract

The experimental field dependences of electron drift velocity in the Al0.3Ga0.7As/GaAs quantum well (QW) have no negative slope region and saturate at electric fields in the range of 5–10 kV/cm. The saturated drift velocity in the narrow (10 nm) QW is lower and in the wide (30 nm) QW is larger than the saturated drift velocity in bulk GaAs. The enhancement of the saturated drift velocity is explained by the decrease in the equivalent intervalley and polar optical phonon scattering rates of electrons in upper valleys of a GaAs conduction band with the increase of a QW width. The calculation of these electron scattering rates shows that in AlGaAs/GaAs QW with a width larger than 10 nm, the total confined electron–phonon scattering rate is lower compared with the electron–phonon scattering rate in bulk GaAs. Correspondingly, the electron drift velocity in AlGaAs/GaAs QW is larger than in bulk GaAs at electric fields higher than 10 kV/cm. Keywords: electron drift velocity, electron–phonon scattering, AlGaAs/GaAs heterostructures