Energy relaxation of hot electrons in GaAs/AlGaAs superlattices measured by infrared differential spectroscopy

The energy relaxation of hot electrons in a strongly coupled, n-type GaAs/AlGaAs superlattice is measured by analysing the temperature and electric-field dependence of the interminiband absorption. Electrons are heated up by an electric-field pulse and the resulting change of the electron temperature is measured by monitoring the spectral change of the infrared absorption. The measured energy-loss rates are higher than predicted by a simple 3D model including acoustic and LO phonon emission. Other possible relaxation channels, such as folded acoustic phonons or coupled plasmon-phonon modes are discussed. An energy relaxation time can be extracted from the power balance and results to vary between 300 ps at 15 K and 20 ps at 48 K. (C) 1997 Academic Press Limited