Resonant Tunneling Spectroscopy of Sidewall-Confined States and Impurity-Bound States Using AlGaAs-GaAs Triple-Barrier Diodes

We have studied resonant tunneling (RT) through AlGaAs-GaAs triple-barrier diodes with diameters between 0.4 µm and 18 µm. We have observed two sets of fine structures just above and below the RT threshold voltage V th in the current-voltage curve of a submicron diode at T=4 K. The magnetic field dependence of the structure set above V th is well fitted by calculation assuming a diode sidewall-depletion confinement. The other set below V th is sample dependent and tends to disappear as the diode becomes smaller, which suggests that their origin is RT through impurity-bound states.