Formation and Characterization of High Density Semiconductor Quantum Dots

我们开发了一种通过选择区域金属有机气相外延(SA-MOVPE)生长来形成位置和尺寸可控的量子线(QWR)和量子点(QD)的技术。该技术被应用于采用QD-QWR耦合结构的单电子晶体管和电路的直接制造。本课题的主要研究成果如下：(1)研究了SA-MOVPE制备高密度、极均匀量子点阵列的机理。我们发现并阐明了SA-MOVPE中的自限机制，即在形成这种三维结构后，保持了GaAs锥体结构和脊状结构的顶部尺寸和形状。这种自限生长模式被用来实现量子点的尺寸均匀。我们还阐明了砷化镓金字塔的顶端尺寸是由台阶边吸附原子和脱附原子之间的平衡决定的，并且可以由生长条件控制。(2)基于织物…结合量子点阵列的更多技术，我们提出并成功地用SA-MOVPE制作了二维量子点和量子阱耦合阵列，光学表征证实了量子点和量子阱形成了网络状的阵列。结果表明，我们提出的制备方法是实现未来电子学中单电子晶体管等量子器件高密度集成的有效方法。(3)将SA-MOVPE技术形成的QWR-QD-QWR耦合结构与肖特基栅极技术相结合，成功地制备了单电子晶体管。我们已经成功地演示了单电子反相器的电路工作，它将量子线晶体管和单电子晶体管一步生长在为SA-MOVPE设计的掩模衬底上。我们的量子点器件也显示出很强的横向限制，这有利于探索纳米结构的物理，如量子点中的近藤效应。较少

We have developed a technique to form position-and size-controlled quantum wires (QWRs) and quantum dots (QDs) by selective area metalorganic vapor phase epitaxial (SA-MOVPE) growth. The technique is applied for the direct fabrication of single electron transistors and circuits using QD-QWR coupled structures. Main results of the project are summarized below.(1) We investigated the mechanism of SA-MOVPE for the fabrication of high-density QD arrays with extreme uniformity. We have found and clarified the self-limited mechanism in SA-MOVPE where the top size and shape of the GaAs pyramidal structures and ridge structures are maintained after the formation of such 3-dimensional structures. This self-limited growth mode is utilized to achieve size uniformity in QDs. We also have clarified that the top size of the GaAs pyramid is determined by the balance between the adsorption and desorption of adatoms at the step edges and can be controled by the growth conditions.(2) Based on the fabric … More ation technique of QD arrays, we have proposed and succes sfully fabricated a two-dimensional coupled array of QDs and QWRs by SA-MOVPE.The optical characterization has confirmed the formation of network-like array of QDs and QWRs. The results indicate that our proposed fabrication method is effective to realize high-density integration of quantum devices, such as single electron transistors, for future electronics.(3) Single electron transistors have successfully been fabricated by the combination of coupled structures of QWR-QD-QWR formed by SA-MOVPE technique and Schottky gate technology. We have succeeded in the demonstration of the circuit operation of single electron inverters, which integrates quantum wire transistor and single electron transistors fabricated by one-step growth on designed masked substrate for SA-MOVPE.Our quantum dot devices also have shown to exhibit strong lateral confinement that are beneficial to explore the physics of nanostructures, such as Kondo effect in QDs. Less