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性质，实现具有可控界面的半导体量子纳米结构。特别是，各种类型的量子纳米结构的制造金属有机气相外延生长（MOVPE）的图案化基板上或邻位基板上的生长。主要结果如下。(1)本文研究了金属有机物气相外延（MOVPE）中在GaAs（001）衬底上生长AlGaAs/GaAs量子点（QD）结构的新方法。图案化的衬底在表面上具有孔阵列，并且这些孔通过MOVPE生长部分地填充有GaAs，然后是GaAs/AlGaAs量子阱结构。对这种图案化衬底上的生长过程的详细研究揭示了Ga和Al在不同刻面之间的复杂二维迁移。GaAs点的形成直接证实了空间分辨阴极发光测量。(2)我们提出了一种新的侧面超晶格（LSSL）型电子干涉器件，其中LSSL的周期通常为60 nm，通过利用邻近GaAs（001）表面上的多原子台阶。考虑到LSSL中的随机性效应，对器件的电导率进行了理论研究。我们还在低温下对它的漏极和漏极特性进行了实验研究，发现gm-V_G特性有明显的振荡，这归因于电子干涉效应。

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.