Transient Hole Trapping in Individual GeSi Quantum Dot Grown on Si(001) Studied by Conductive Atomic Force Microscopy

Electrical properties of individual self-assembled GeSi quantum dots grown on Si substrates are investigated by using conductive atomic force microscopy at room temperature. By controlling the bias voltage sweep in a certain fast sweep rate range, a novel current peak is observed in the current--voltage characteristics of the quantum dots. The current peaks are detectable 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 current--voltage characteristic under fast sweep is very different from the ordinary steady state current behaviour of quantum dots measured previously. The origin of this phenomenon can be attributed to the transient hole trapping in the potential well formed by the quantum dot sandwiched between the native oxide layer and the bottom Si substrate.