Resonant tunneling of electrons through single self-assembled InAs quantum dot at room temperature studied with conductive AFM tip

Resonant tunneling of electrons through a quantum level in a self-assembled InAs quantum dot (QD) has been measured by conductive atomic force microscopy (AFM) at room temperature. InAs QDs are embedded in a 3.4 nm-thick AlAs layer, and capped with 8.3 nm-thick GaAs layer on which surface InAs QDs are deposited as nano-scale electrodes. Bringing the conductive AFM tip on the surface InAs QD which should be vertically aligned with a buried QD, a bias voltage is applied to the sample, and a current flowing via the buried QD is measured. Negative differential resistance attributed to electron resonant tunnelling through a quantized energy level in the buried QD is observed in the current-voltage characteristics. The voltage loss by nano-scale electrode and the dependence of resonance voltage on the size of the surface QD-electrodes are discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)