Single-electron tunneling in double-barrier nanostructures

We have observed single-electron charging of the well in nanometer double-barrier resonant tunneling devices. Asymmetric heterostructure material was used so that one barrier is less transparent than the other. Resonant tunneling through size-quantized well states and the single-electron charging are thus largely separated in the two bias polarities. When the emitter barrier is more transparent than the collector barrier, electrons accumulate in the well; incremental electron occupation of the well, starting from zero, is accompanied by Coulomb blockade, which leads to sharp steps of the tunneling current. The voltage extent of the steps is affected by the intrawell electron-electron interaction. When the emitter barrier is less transparent, the current reflects resonant tunneling of just one electron at a time through size quantized well states; the current peaks and/or steps (depending on experimental parameters) appear in current-voltage characteristics.