Tuning of tunneling rates in quantum dots using a quantum point contact

We study the influence of asymmetric tunneling rates of a lateral quantum dot connected to source and drain leads. We use a quantum point contact (QPC) to detect charging events on the dot. Since the mean charge depends on the ratio of the tunneling rates the QPC can be used to detect symmetric configurations where both rates are equal. Thus, the transport properties of the dot can be investigated concerning this symmetry. We concentrate on the visibility of features that correspond to transitions with excited states. We interpret the results with the number of channels used for transport, the electron flow direction and the rate symmetry. (c) 2006 Elsevier B.V. All rights reserved.