Self-Organization Mechanism and Electronic Properties of Semiconductor Quantum Dots

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The conductive scanning probe microscope (SPM) technique was used in order to study the electronic properties and self-organization mechanism of InGaAs quantum dots (QDs) grown on GaAs (311)B substrates. The QDs were fabricated by atomic H-assisted molecular beam epitaxy, and Si SPM tips coated with Au, which warrants electrical conductivity were used to measure both the topographic and current images of QDs surface simultaneously. The conductive SPM measurements were performed in vacuum at room temperature and at lowered temperatures. With this technique, the single-electron tunneling events in the QDs of varying sizes, and of any other arbitrary positions on the QDs surface can be studied by using the same conductive AFM tip. It was found that (1) the center of a QD is more conductive than its periphery, and (2) the surface. in between the QDs is highly resistive. The differences in the conductance were due to the local modification of surface bending associated with the surface states. Further, it was found that the conductance becomes spatially uniform at all points over the packed and ordered QDs at low temperatures, which could be explained by lateral coupling of these strained QDs