Dynamics of injected electron cooling in GaAs

Using the technique of hot-electron spectroscopy we have measured the change in hot-electron spectra with transit region width enabling us to obtain a dynamic picture of injected hot-electron cooling in n+ GaAs. All features in the spectra have been identified and ‘‘ballistic’’ transport has been observed for samples having narrow transit region widths (<850 Å) while near diffusive transport has been observed for samples having wide transit region widths (>1700 Å). With increasing transit region width, rather than the electron distribution shifting en masse to lower energies, electrons are removed from the initial injected peak and scattered to lower energies close to the Fermi energy. This process of electron cooling is dramatically illustrated by measuring the magnetic field dependence of the hot-electron spectra.