Imaging and probing electronic properties of self-assembled InAs quantum dots by atomic force microscopy with conductive tip

Atomic force microscopy with a conductive probe has been used to study both the topography and the electronic properties of 10-nm-scale self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy on n-type GaAs. Th e current flowing through the conductive probe normal to the sample surface is measured for imaging local conductance, while the deflection of cantile ver is optically detected for disclosing geometrical structure. The conduct ance on InAs QDs is found to be much larger than that on the wetting layer, allowing imaging of QDs through measurements of local current. We attribut e this change in conductance to the local modification of surface band bend ing associated with surface states on InAs QD surface. Mechanisms of electr on transport through QDs are discussed based on current-voltage characteris tics measured on QDs of various sizes. (C) 1999 American Institute of Physi cs. [S0003-6951(99)03206-4].