Self-Organization Mechanism and Electronic Properties of Semiconductor Quantum Dots

利用电导扫描探针显微镜(SPM)技术研究了生长在GaAs(311)B衬底上的InGaAs量子点的电学性质和自组织机制。利用氢原子辅助分子束外延技术制备了量子点，并用具有良好导电性的Au包覆的Si SPM探针同时测量了量子点表面的形貌和电流图像。电导SPM测量是在室温和低温下在真空中进行的。利用这种技术，可以用相同的导电原子力显微镜针尖来研究不同尺寸的量子点中的单电子隧穿事件，以及量子点表面任何其他位置的单电子隧穿事件。结果表明：(1)量子点中心的导电性强于其外围，(2)表面。在量子点之间是高度电阻性的。电导的差异是由于与表面态相关的表面弯曲的局部修正所致。此外，还发现在低温下，填充有序的量子点上的电导在所有点上都变得均匀，这可以用这些应变量子点的横向耦合来解释

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