Metastable excited states of a closed quantum dot probed by an aluminum single-electron transistor

Abstract

Kinetics of a closed quantum dot (QD) in a GaAs AlGaAs heterostructure crystal are studied by probing the current through an aluminum single-electron transistor fabricated on top of the QD. Distinctly different characteristics of the Coulomb blockade oscillations are found in different gate bias conditions, indicating different regimes of the isolated QD. An excited state of the QD, where the electrostatic potential is significantly lifted up, as well as another excited state, where the electrostatic potential is significantly pulled down, are suggested. Both of the states are characterized by an extremely long life time roughly about 20 min. A model is proposed to consistently explain these states. © 2006 The American Physical Society.