Tunneling measurements of symmetric-interface phonons in GaAs/AlAs double-barrier structures

In this paper we report the results of extensive magnetotransport experiments on asymmetric GaAs/AlAs double-barrier structures that were specifically designed to possess large phonon-assisted tunneling currents. We find quantitative agreement between measured valley currents at liquid-helium temperature and calculations that include the effects of phonon localization using the dielectric-continuum model. The results demonstrate that (1) a major part of the valley current in these structures is due to phonon-assisted tunneling, and (2) symmetric-interface phonons and confined phonons in the GaAs well are the most important in phonon-assisted tunneling processes. Charge buildup in the GaAs well is found to shift current-voltage curves to higher voltages and to distort magnetic field versus applied voltage diagrams.