Quantum Interference Effect in Semiconductor quantum wires and applications to electron wave devices

微制造技术的最新进展使制造亚微米或更小尺寸的器件成为可能。这些尺寸小于电子相位相干长度和弹性散射长度，各种量子干涉效应变得清晰可见。旨在揭示这些效应的机制和寻找新的量子效应的基础研究被称为介观物理，正在成为物理学研究的一个重要领域。同时，这项研究对未来的电子器件或电子波器件也具有重要的意义，它们的产生原理与目前的器件有很大的不同。本研究旨在研究半导体内观结构中的量子输运效应，为未来的器件应用奠定重要的基础。本研究所用材料为GaAs、GaAlAs/GaAlAs异质结。取得的主要成果如下：(1)研制了低能聚焦离子束系统，并研究了其辐照损伤。我们发现，当束流能量低于1keV时，可以实现低损伤过程。(2)比较了Ar离子研磨和CC12F2反应离子刻蚀(RIE)制备的GaAs/GaAlAs量子线的损伤效应对非弹性散射长度(LIN)的影响，发现反应离子刻蚀(RIE)产生的损伤较小，非弹性散射长度(LIN)较长。(3)研究了弹道输运效应，发现具有较大的弯曲阻力和负阻。从这些阻力的衰减中，我们发现弹道输运的特征长度比弹性散射长度短得多。(4)研究了样品形状、辐射损伤和量子输运效应的影响。我们制作了一种具有平面侧栅结构的FET，并展示了控制量子输运的可能性，这对器件的应用具有重要意义。

Recent advances in microfabrication techniques have made it possible to produce devices with submicron or smaller dimensions. These dimensions are smaller than the electron phase coherence length and elastic scattering length and various quantum interference effects becomes clearly observable. Basic research aiming to reveal the mechanisms of these effects and to search for new quantum effects is called "mesoscopic physics" and is becoming an important field in physics research. At the same time, the research is also important for future electronic devices or electron wave devices, which create functions by quite different principles from the present devices.The present study aims to study the quantum transport effect in semiconducter nesoscopic structure which is important to establish basics for future device applications. Materials used in the present study were GaAs, GaAs/GaAlAs heterostructures. The major achievements are summarized as follows.(1) Low energy focused ion beam system was fabricated and radiation damage was investigated in GaAs. We found that low damage process is possible for beam energy lower than lkev. (2) We compared damage effect on inelastic scattering length (lin) in GaAs/GaAlAs quantum wires fabricated using Ar ion milling and CC12F2 reactive ion etching (RIE) and found that the RIE induces less damage and gives longer lin (3) We studied ballistic transport effects and found large bend resistance and negative resistance. From the decay of these resistance, we found that the characteristic length for ballistic transport is much shorter than the elastic scattering length. (4) The effect of sample shape and radiation damage an the quantum transport effect was investigated. We fabricated FET's which has a new structure with plannar side gates and showed the possibility to control the quantum transport which is important for device applications.