## Abstract

Semiconductor nanowires fabricated by a bottom-up approach are not only interesting for the realization of future nanoscaled devices but also appear to be very attractive model systems to tackle fundamental questions concerning the transport in strongly confined systems. In order to avoid the problem connected with carrier depletion, narrowband gap semiconductors, i.e., InAs or InN, or core-shell Nanowires, i.e., GaAs/AlGaAs, are preferred. The underlying reason is that in InAs or InN the Fermi-level pinning in the conduction band results in a carrier accumulation at the surface. In fact, the tubular topology of the surface electron gas opens up the possibility to observe unconventional quantum transport phenomena. When the phase-coherence length in the nanowire is comparable to its dimensions the conductance fluctuates if a magnetic field is applied or if the electron concentration is changed by means of a gate electrode. These so-called universal conductance fluctuations being in the order of e{sup 2}/h originate from the fact that in small disordered samples, electron interference effects are not averaged out. In this work are analyzed universal conductance fluctuations to study the quantum transport properties in InN, InAs and GaAs/AlGaAs nanowires. With the use of a magnetic field and a back-gate electrode the
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## Citation Formats

Estevez Hernandez, Sergio.
Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten.
Germany: N. p.,
2009.
Web.

Estevez Hernandez, Sergio.
Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten.
Germany.

Estevez Hernandez, Sergio.
2009.
"Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten."
Germany.

@misc{etde_21317711,

title = {Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten}

author = {Estevez Hernandez, Sergio}

abstractNote = {Semiconductor nanowires fabricated by a bottom-up approach are not only interesting for the realization of future nanoscaled devices but also appear to be very attractive model systems to tackle fundamental questions concerning the transport in strongly confined systems. In order to avoid the problem connected with carrier depletion, narrowband gap semiconductors, i.e., InAs or InN, or core-shell Nanowires, i.e., GaAs/AlGaAs, are preferred. The underlying reason is that in InAs or InN the Fermi-level pinning in the conduction band results in a carrier accumulation at the surface. In fact, the tubular topology of the surface electron gas opens up the possibility to observe unconventional quantum transport phenomena. When the phase-coherence length in the nanowire is comparable to its dimensions the conductance fluctuates if a magnetic field is applied or if the electron concentration is changed by means of a gate electrode. These so-called universal conductance fluctuations being in the order of e{sup 2}/h originate from the fact that in small disordered samples, electron interference effects are not averaged out. In this work are analyzed universal conductance fluctuations to study the quantum transport properties in InN, InAs and GaAs/AlGaAs nanowires. With the use of a magnetic field and a back-gate electrode the universal conductance fluctuations and localizations effects were analyzed. Since InN and InAs are narrow band gap semiconductors, one naturally expects spin-orbit coupling effects. Because this phenomena is of importance for spin electronic applications. However, owing to the cylindrical symmetry of the InN and InAs nanowires, the latter effect was observable and actually be used to determine the strength of spin-orbit coupling. In order to clearly separate the weak antilocalization effect from the conductance fluctuations, the averaging of the magnetoconductance at different gate voltages was essential. The low-temperature quantum transport properties of gated InN, InAs and GaAs/AlGaAs nanowires were investigated. Magnetic field-dependent as well as gate-dependent measurements of universal conductance fluctuations were performed to gain information on the phase coherence in the electron transport. In this work was found a pronounced decrease in the variance of the conductance by about a factor of 2 in gate-dependent fluctuation measurements if a magnetic field is applied. This effect is explained by the suppression of the Cooperon channel of the electron correlation contributing to the conductance fluctuations. Despite the fact that the diameter of the nanowire is less than 100 nm a clear weak antilocalization effect is found in the averaged magnetoconductance being in strong contrast to the suppression of weak antilocalization for narrow quantum wires based on planar two-dimensional electron gases. The unexpected robustness of the weak antilocalization effect observed here is attributed to the tubular topology of the surface electron gas in InN and InAs nanowires. (orig.)}

place = {Germany}

year = {2009}

month = {Oct}

}

title = {Phase-coherent transport and spin-orbit-coupling in III/V-semiconductor nanowires; Phasenkohaerenter Transport und Spin-Bahn-Wechselwirkung in III/V-Halbleiternanodraehten}

author = {Estevez Hernandez, Sergio}

abstractNote = {Semiconductor nanowires fabricated by a bottom-up approach are not only interesting for the realization of future nanoscaled devices but also appear to be very attractive model systems to tackle fundamental questions concerning the transport in strongly confined systems. In order to avoid the problem connected with carrier depletion, narrowband gap semiconductors, i.e., InAs or InN, or core-shell Nanowires, i.e., GaAs/AlGaAs, are preferred. The underlying reason is that in InAs or InN the Fermi-level pinning in the conduction band results in a carrier accumulation at the surface. In fact, the tubular topology of the surface electron gas opens up the possibility to observe unconventional quantum transport phenomena. When the phase-coherence length in the nanowire is comparable to its dimensions the conductance fluctuates if a magnetic field is applied or if the electron concentration is changed by means of a gate electrode. These so-called universal conductance fluctuations being in the order of e{sup 2}/h originate from the fact that in small disordered samples, electron interference effects are not averaged out. In this work are analyzed universal conductance fluctuations to study the quantum transport properties in InN, InAs and GaAs/AlGaAs nanowires. With the use of a magnetic field and a back-gate electrode the universal conductance fluctuations and localizations effects were analyzed. Since InN and InAs are narrow band gap semiconductors, one naturally expects spin-orbit coupling effects. Because this phenomena is of importance for spin electronic applications. However, owing to the cylindrical symmetry of the InN and InAs nanowires, the latter effect was observable and actually be used to determine the strength of spin-orbit coupling. In order to clearly separate the weak antilocalization effect from the conductance fluctuations, the averaging of the magnetoconductance at different gate voltages was essential. The low-temperature quantum transport properties of gated InN, InAs and GaAs/AlGaAs nanowires were investigated. Magnetic field-dependent as well as gate-dependent measurements of universal conductance fluctuations were performed to gain information on the phase coherence in the electron transport. In this work was found a pronounced decrease in the variance of the conductance by about a factor of 2 in gate-dependent fluctuation measurements if a magnetic field is applied. This effect is explained by the suppression of the Cooperon channel of the electron correlation contributing to the conductance fluctuations. Despite the fact that the diameter of the nanowire is less than 100 nm a clear weak antilocalization effect is found in the averaged magnetoconductance being in strong contrast to the suppression of weak antilocalization for narrow quantum wires based on planar two-dimensional electron gases. The unexpected robustness of the weak antilocalization effect observed here is attributed to the tubular topology of the surface electron gas in InN and InAs nanowires. (orig.)}

place = {Germany}

year = {2009}

month = {Oct}

}