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(40) Production(s) de CHAUBET C.
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Conduction electrons localized by charged magnetoacceptors A2- in GaAs/GaAlAs quantum wells
Auteur(s): Kubisa M, Ryczko K., Bisotto Isabelle, Chaubet C., Raymond A., Zawadzki W
(Article) Publié:
-Physical Review B Condensed Matter And Materials Physics (1998-2015), vol. 92 p.035409 (2015)
Texte intégral en Openaccess :
Ref HAL: hal-01174748_v1
DOI: 10.1103/PhysRevB.92.035409
WoS: 000357486400006
Exporter : BibTex | endNote
3 Citations
Résumé: A variational theory is presented of A1− and A2− centers, i.e., of a negative acceptor ion localizing one and two conduction electrons, respectively, in a GaAs/GaAlAs quantum well in the presence of a magnetic field parallel to the growth direction. A combined effect of the well and magnetic field confines conduction electrons to the proximity of the ion, resulting in discrete repulsive energies above the corresponding Landau levels. The theory is motivated by our experimental magnetotransport results which indicate that, in a heterostructure doped in the GaAs well with Be acceptors, one observes a boil-off effect in which the conduction electrons in the crossed-field configuration are pushed by the Hall electric field from the delocalized Landau states to the localized acceptor states and cease to conduct. A detailed analysis of the transport data shows that, at high magnetic fields, there are almost no conducting electrons left in the sample. It is concluded that one negative acceptor ion localizes up to four conduction electrons.
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AC-magnetotransport of a 2DEG in the quantum Hall regime
Auteur(s): Hernandez Carlos, Consejo C., Chaubet C.
Conference: 7TH INTERNATIONAL CONFERENCE ON LOW DIMENSIONAL STRUCTURES AND DEVICES: (LDSD 2011) (Telchac, MX, 2011-05-22)
Actes de conférence: AIP Proceedings, vol. 1598 p.218 (2014)
Ref HAL: hal-01071270_v1
DOI: 10.1063/1.4878312
WoS: 000341459700047
Exporter : BibTex | endNote
Résumé: In this paper we present an ac-magneto-transport study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime, for frequencies in the range [100Hz, 1MHz]. We present a new approach to understand admittance measurements based in the Landauer-Buttiker formalism for QHE edge channels and taking into account the capacitance and the topology of the cables connected to the contacts used in the measurements. Our model predicts an universal behavior with the a-dimensional parameter RCω where R is the 2 wires resistance of the 2DEG, C the capacitance cables and the angular frequency, in agreement with experiments
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Admittance measurements in the quantum Hall effect regime
Auteur(s): Hernandez Carlos, Consejo C., Chaubet C.
Conference: XXII International Material Research Congress (IMRC 2013) (Cancun, MX, 2013-08-11)
Actes de conférence: Physica B: Condensed Matter, vol. 453 p.153-157 (2014)
Ref HAL: hal-01065652_v1
Exporter : BibTex | endNote
Résumé: In this work we present an admittance study of a two-dimensional electron gas(2DEG) in thequantum Hall effect (QHE) regime. We have studied several Hall bars in different contacts configurations in the frequency range100Hz-1 MHz. Our interpretation is based on the Landauer-Büttiker theory and takes into account both the capacitance and the topology of the coaxial cables which are connected to the sample holder. We show that we always observe losses through the capacitive impedance of the coaxial cables, except in the two contacts configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the 2DEG and show its dependence with the filling factor ν.
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Admittance of multiterminal quantum Hall conductors at kilohertz frequencies
Auteur(s): Hernandez Carlos, Consejo C., Degiovanni Pascal, Chaubet C.
(Article) Publié:
Journal Of Applied Physics, vol. 115 p.123710 (2014)
Ref HAL: hal-01065647_v1
DOI: 10.1063/1.4869796
WoS: 000333901100042
Exporter : BibTex | endNote
4 Citations
Résumé: We present an experimental study of the low frequency admittance of quantum Hall conductors in the [100 Hz, 1 MHz] frequency range. We show that the frequency dependence of the admittance of the sample strongly depends on the topology of the contacts connections. Our experimental results are well explained within the Christen and Büttiker approach for finite frequency transport in quantum Hall edge channels taking into account the influence of the coaxial cables capacitance. In the Hall bar geometry, we demonstrate that there exists a configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the sample and observe its dependence on the filling factor.
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Two-electron states localized by charged acceptors in GaAs/GaAlAs quantum wells in ultra-quantum regime of magnetic fields
Auteur(s): Bisotto I, Chaubet C., Raymond A., Zawadzki W, Kubisa M
Conference: EP2DS: 20th International Conference on Electronic Properties of Two-Dimensional Systems (2013) (Wroclaw, PL, 2013-07-01)
Ref HAL: hal-00943352_v1
Exporter : BibTex | endNote
Résumé: We demonstrate theoretically that bound acceptors states of a two dimensional electron gas in quantizing magnetic field can localize two electrons on a same site. We calculate the energies and wave functions of the second quantum state, and show that they are close to calculations of the first quantum state found previously.
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Highly sensitive nanohall sensors on GaAlAs/GaAs heterojunctions
Auteur(s): Chaubet C., Chenaud B., Pascal F., Hoffmann A., Feltin N.
Conference: 2013 22nd International Conference on Noise and Fluctuations (ICNF) (Montpellier, FR, 2013-06-24)
Ref HAL: hal-00940145_v1
DOI: 10.1109/ICNF.2013.6578883
Exporter : BibTex | endNote
Résumé: We present an experimental study on the performance of nano-Hall sensors made on the two dimensional electron gaz of a pseudo morphic GaAlAs/GaInAs heterostructures. The active area of the sensor is from sub-micronic scale (down to 500 nm) to 5 microns. Ohmic contacts have micronic size, and a reference sample of 80 micron width has been caracterized as well, as a reference. In our process, we have improved the contacts technology to limit the thermal Shottky noise. Thus although ohmic contacts have small dimensions they have low resistance and do not limit the sensitivity of our nano-sensors. Extensive caracterization of those devices demonstrate a diffusive transport at 300 K, and a magnetic field sensitivity up to 1000 V/T/A. We have focused our attention on the smallest detectable magnetic field in the smallest sensor, and performed a systematic study of the noise measurements. We have measured the excess noise in both the longitudinal configuration and the Hall configuration, as a function of the current. Our noise measurements performed at room temperature in the range [1 Hz-100 kHz] show, at low frequency, an 1/f noise spectrum whose intensity is proportional to the square of the current. We understand our data by the conductivity fluctuations model and we obtain the Hooge parameter for this technology. We demonstrate that the noise intensity is inversely proportional to area of the sensor. Of course reducing the dimensions induces physical limitations but we demonstrate that a magnetic field of few μT can be measured with a micron scale sensor at low frequencies; at higher frequencies, when the thermal noise limits the resolution, the measurement of 300 nT is achievable
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Low Frequency Admittance Measurements in the Quantum Hall Regime
Auteur(s): Chaubet C., Hernandez Carlos
Conference: 2013 IMRC Meeting (Cancun, MX, 2013-08-11)
Actes de conférence: MRS Online Proceedings Library, vol. 1617 p.26 (2013)
Ref HAL: hal-00933374_v1
DOI: 10.1557/opl.2013.1187
Exporter : BibTex | endNote
Résumé: In this paper we present an ac-magneto-transport study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime, for frequencies in the range [100Hz, 1MHz]. We present an approach to understand admittance measurements based in the Landauer-Buttiker formalism for QHE edge channels and taking into account the capacitance and the topology of the cables connected to the contacts used in the measurements. Our model predicts an universal behavior with the a-dimensional parameter R H Cω where R H is the 2 wires resistance of the 2DEG, C the capacitance cables and the angular frequency, in agreement with experiments. For a specific configuration, we measure the electrochemical capacitance of the quantum Hall edge channels as predicted by Christen and Büttiker.
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