Direct observation of the hot electron distribution function in GaAs/AlGaAs heterostructures

Abstract

A new direct experimental technique to study the form of the hot electron distribution function is presented. Far infrared emission induced by a weak periodic potential is observed in high-mobility GaAs/AlGaAs heterostructures with extremely low electron density. The electric-field-dependent spectra give for the first time evidence of a nonequilibrium shape of the electronic distribution in the electric field direction. The onset of LO-phonon emission is clearly observed. Perpendicular to the applied electric field, a smooth form of the distribution is found. The results agree well with theoretical distribution functions obtained from the Boltzmann transport equation.