SINGLE-ELECTRON TUNNELING AND COULOMB CHARGING EFFECTS IN ASYMMETRIC DOUBLE-BARRIER RESONANT-TUNNELING DIODES

Resonant tunneling is studied in an ultrasmall asymmetric GaAs-AlxGa1-xAs double-barrier diode at low temperatures. In reverse bias, spikelike current-voltage characteristics are observed and assigned to electrons tunneling from zero-dimensional (OD) states in the accumulation layer to OD states in the well. The OD-OD tunneling reflects the single-electron spectrum without Coulomb charging effects. In forward bias, steplike current-voltage characteristics are observed and ascribed to tunneling from one-dimensional subbands in the emitter contacts through OD states in the well, accompanied by Coulomb charging effects. A moderate magnetic field (B almost-equal-to 4 T) parallel to the current improves the flatness of the plateaus.