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

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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.