Fabrication of Ultrasmall Compound Semiconductor Nanostructures with Controlled Interfaces and Characterization of Their Electronic Properties

本研究的目的是利用晶体生长的自组织特性，实现界面可控的半导体量子纳米结构。特别是，通过金属-有机气相外延生长(MOVPE)在图案化衬底或邻近衬底上生长制备了各种类型的量子纳米结构。主要研究结果如下：(1)研究了金属-有机气相外延(MOVPE)在图案化的GaAs(001)衬底上的生长过程，提出了一种制备AlGaAs/GaAs量子点(QD)结构的新方法。图案化的衬底表面有一系列的空穴，这些空穴通过MOVPE生长部分填充了GaAs层，然后是GaAsAlGaAs量子阱结构。对这种图案化衬底上生长过程的详细研究表明，Ga和Al在不同面间存在复杂的二维迁移。空间分辨阴极发光测量直接证实了GaAs点的形成。(2)我们提出了一种新的横向表面超晶格(LSSL)型电子干涉器件，其周期通常为60 nm。从理论上研究了器件的导电性，并考虑了大尺寸固体激光器中随机性的影响。我们还对其低温下的漏极和跨导特性进行了实验研究，发现Gm-V_G特性出现了明显的振荡，这归因于电子干扰效应。

The objective of the present research is to realize semiconductor quantum nanostructures with controlled interfaces by utilizing the self-organized nature of the crystal growth. In particular, various types of quantum nanostructures were fabricated by metal-organic vapor phase epitaxial growth (MOVPE) growth on patterned substrates or on vicinal substrates. The main results are listed below.(1) We studied on a growth process on patterned GaAs (001) substrate during metal-organic vapor phase epitaxy (MOVPE) and a novel approach for the fabrication of AlGaAs/GaAs quantum dot (QD) structures. The patterned substrate have an array of holes on the surface and those holes are partially filled with GaAs by MOVPE growth, followed by GaAs/AlGaAs quantum well structures. Detailed investigation on growth process on such patterned substrates revealed the presence of complicated two-dimensional migration of Ga and Al between different facets. Formation of GaAs dots was directly confirmed by spatially resolved cathodoluminescence measurements.(2) We propose a new, lateral surface superlattice (LSSL) type of electron interference devices, where the period of LSSL is typically 60nm, by utilizing multiatomic steps on a vicinal GaAs (001) surface. Conductivity of the device is theoretically studied by taking the effect of randomness in the LSSL into account. We also investigate its drain and transconductance characteristics experimentally at low temperatures, and found clear oscillations in gm-V_G characteristics, which were ascribed to the electron interference effect.