Transport électronique quasi-balistique dans les nanofils d’InAs et d’InSb sous champ magnétique intense

Abstract : InAs and InSb nanowires, fabricated by epitaxial growth, represent an electron gas confined in a 1D conductor with many advantages such as high mobility and a strong spin-orbit coupling. However a lack of experimental characterization of their band structure remains. In this thesis the electronic properties are studied experimentally by measuring the electronic transport in the quasi-ballistic regime and under magnetic field up to 55 T. The quasi-ballistic regime is highlighted by the conductance quantization between the temperatures of 2 K to 50 K. The band structure is probed by analyzing the conductance plateaus as a function of the gate voltage, the bias voltage, and the magnetic field. The results show good agreements with band structure simulations. Other information, such as transmission, field effect mobility and gate capacitance, is extracted. The application of a magnetic field lifts the orbital and spin degeneracy. Under a magnetic field perpendicular to the nanowire axis subbands evolved towards Landau quantization together with backscattering reduction. The ballistic regime is prominent under strong magnetic fields and allows the determination of the transmission of the contacts. Fluctuations of the magneto-conductance are observed in function of magnetic field parallel to the nanowire axis. They reveal the carriers confinement within the nanowire and Landau orbits emergence in the transport direction. The coherent electron transport is jointly studied in these systems. It is highlighted by the observation of universal conductance fluctuations and electronic Fabry-Pérot oscillations. Finally the low-temperature photoconductivity is measured under illumination for wavelengths close to the band gap energy. In this exploratory work, photoconductivity measurement reveals the presence of Schottky barriers at the contacts and unexpected anisotropy according to the direction of linear polarization for InSb Zinc Blende nanowires.
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Submitted on : Tuesday, December 6, 2016 - 6:16:52 PM
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  • HAL Id : tel-01408276, version 1

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Florian Vigneau. Transport électronique quasi-balistique dans les nanofils d’InAs et d’InSb sous champ magnétique intense. Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]. Institut national des sciences appliquées de Toulouse, 2016. Français. ⟨tel-01408276⟩

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