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Electrical properties of individual self-assembled Ge quantum dots grown on Si substrate are investigated by using conductive atomic force microscopy at room temperature. By scanning the bias voltage in a certain fast sweep rate range, a novel current peak is observed in the current-voltage characteristics measured on individual Ge quantum dots. The current peaks are detected only during the backward voltage sweep immediately after a forward sweep. The current peak position and intensity are found to depend strongly on the voltage sweep conditions. This kind of fast sweep current-voltage characteristic is very different from the ordinary steady state current behaviors of quantum dots measured previously. The origin of this phenomenon is attributed to the transient carrier trapping in the potential well formed by the quantum dot sandwiched between the top oxide layer and bottom Si substrate. |