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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We have developed a scanning type of noise sensor system, which utilizes the detection of local voltage fluctuations with a quantum Hall effect (QHE) electrometer. This technique has enabled us to produce the first image of a noise-voltage distribution in a QHE sample. The experimental data clearly reveal that a large amount of noise occurs in the lower magnetic field region of a QHE plateau of Landau-level-filling factor 2 and that it is concentrated in a high-potential edge region of the Hall bar sample. These findings can be reasonably explained as originating from unstable electron transfer taking place when the nonequilibrium edge state equilibrates with the bulk state. These results identify our sensor system as a unique probe of nonequilibrium edge states in QHE systems. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.2149221

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We have developed a scanning type of noise sensor system, which utilizes the detection of local voltage fluctuations with a quantum Hall effect (QHE) electrometer. This technique has enabled us to produce the first image of a noise-voltage distribution in a QHE sample. The experimental data clearly reveal that a large amount of noise occurs in the lower magnetic field region of a QHE plateau of Landau-level-filling factor 2 and that it is concentrated in a high-potential edge region of the Hall bar sample. These findings can be reasonably explained as originating from unstable electron transfer taking place when the nonequilibrium edge state equilibrates with the bulk state. These results identify our sensor system as a unique probe of nonequilibrium edge states in QHE systems. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.2149221

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

We have studied the channel-size dependence of nonequilibrium electrons excited into higher Landau levels in a quantum Hall conductor, by mapping cyclotron emission in Hall bars of different sizes. The images obtained reveal that the spatial evolution of the nonequilibrium electrons with current density significantly depends on the channel width of the Hall bar on a macroscopic scale of several hundred mu ms. This observation provides clear evidence of a macroscopic channel-size effect, which can be reasonably understood as originating from a very long equilibrium length of the excited electrons.

DOI： 10.1103/PhysRevLett.95.166801

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

We have studied the channel-size dependence of nonequilibrium electrons excited into higher Landau levels in a quantum Hall conductor, by mapping cyclotron emission in Hall bars of different sizes. The images obtained reveal that the spatial evolution of the nonequilibrium electrons with current density significantly depends on the channel width of the Hall bar on a macroscopic scale of several hundred mu ms. This observation provides clear evidence of a macroscopic channel-size effect, which can be reasonably understood as originating from a very long equilibrium length of the excited electrons.

DOI： 10.1103/PhysRevLett.95.166801

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

We present an experimental investigation of separate distributions of intra- and inter-Landau-level scattering (LLS) in a quantum Hall bar, through the combined use of local voltage sensing and cyclotron emission imaging. The images obtained reveal that the two scatterings are in marked contrast: intra-LLS occurs over the whole channel while inter-LLS is localized in two hot spots and around the source contact. This suggests a substantial difference in the two scattering processes and their characteristic length scale, which is consistent with the expectation from earlier reports.

DOI： 10.1103/PhysRevB.70.081308

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

We present an experimental investigation of separate distributions of intra- and inter-Landau-level scattering (LLS) in a quantum Hall bar, through the combined use of local voltage sensing and cyclotron emission imaging. The images obtained reveal that the two scatterings are in marked contrast: intra-LLS occurs over the whole channel while inter-LLS is localized in two hot spots and around the source contact. This suggests a substantial difference in the two scattering processes and their characteristic length scale, which is consistent with the expectation from earlier reports.

DOI： 10.1103/PhysRevB.70.081308

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We have constructed a scanning electrometer employing a quantum Hall effect (QHE) device. This technique uses capacitive coupling between sensor and sample to read out a change of longitudinal resistance of the sensor. This sensing mechanism was confirmed by measuring the magnetic field dependence of the readout signal and by an analysis based on a model of parallel-plate capacitor. Spatial mapping of Hall voltage profiles in the QHE state was demonstrated with this system. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1647691

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We have constructed a scanning electrometer employing a quantum Hall effect (QHE) device. This technique uses capacitive coupling between sensor and sample to read out a change of longitudinal resistance of the sensor. This sensing mechanism was confirmed by measuring the magnetic field dependence of the readout signal and by an analysis based on a model of parallel-plate capacitor. Spatial mapping of Hall voltage profiles in the QHE state was demonstrated with this system. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1647691

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記述言語：日本語   出版者・発行元：アグネ技術センタ-  

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

Images of the spatial distribution of nonequilibrium electrons are studied in a wide quantum Hall effect (QHE) Hall bar (nu=2) by detecting the local profile of the cyclotron radiation with an improved spatial resolution of 50 mum for the radiation wavelength of lambda=120 mum. The experiments, along with conventional studies of voltage distribution via voltage probes, reveal the generation of nonequilibrium carriers at the diagonally opposite corners of Hall bars (hot spots) at low current levels (below 80 muA), as well as the occurrence of additional generation of nonequilibrium carriers at the corner opposite to the hot spot on the side of the source contact at higher currents (above 80 muA). The experimental findings are consistently interpreted in terms of earlier models of the electron dynamics around current contacts, providing support to the model of bootstrap-type electron heating for the breakdown of the QHE.

DOI： 10.1103/PhysRevB.68.085328

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Far-infrared (FIR) photoconductivity induced by cyclotron resonance in edge slates of quantum Hall devices are studied by carrying out time-resolved measurements. It is found that the recombination of electron-hole pairs excited via cyclotron resonance in edge states is significantly suppressed, yielding a surprisingly long recombination lifetime ( similar to 10 ms). This is in marked contrast to much shorter recombination lifetimes ( similar to 1 ms) in bulk states. The experimental results lead us to suggest that the edge-state FIR photoconductivity is induced by an effect of electric polarization. This implies also that edge states can be a promising candidate for application as a FIR detector. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)00250-2

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記述言語：英語   出版者・発行元：AMER INST PHYSICS  

We studied far-infrared (FIR) response due to cyclotron resonance (CR) of two-dimensional electron gas systems in GaAs/AlGaAs heterostructures by using cyclotron radiation from n-InSb devices as the illumination source. We examined the dependence of the FIR response on different experimental parameters, including the aspect ratio of Hall bars, electron mobility, bias current, illumination intensity, magnetic field, and lattice temperature. A strong photoresponse emerges only in the vicinity of integer quantum Hall effect (IQHE) regimes. Time-resolved measurements show that the recombination lifetime of excited carriers depends largely on the electron mobility, ranging from 5 mus to 1 ms at 4.2 K. The temporal decay of photoresponse is nonexponential in higher-mobility samples, whereas it is exponential with a single time constant in lower-mobility samples. This, together with the relatively large time constants, suggests that the FIR response is induced through multitrapping processes, in which excited carriers in Landau levels are repeatedly captured by localized states and reexcited to delocalized states. This multitrapping process is suggested to be promoted by the CR-induced heating of the electron system. Theoretical calculation based on the electron heating model reasonably reproduces characteristic dependence of the photoresponse on the magnetic field in the vicinity of IQHE plateaus. The IQHE Hall bars serve as a high-sensitive narrow-band FIR detector, where the highest sensitivity reaches similar to 10(8) V/W. Tunability of the detector is demonstrated by varying the electron density. We discuss briefly the design of high-sensitive FIR detectors using the IQHE Hall bars. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1352685

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記述言語：英語   出版者・発行元：SPRINGER-VERLAG BERLIN  

Far IR photoresponse of QHE device operating at cyclotron resonance has been investigated. The possibility of the detector band tuning at the simultaneous increase of the magnetic field and the 2D electron concentration (the latter due to the persistent photoconductivity after band-gap illumination) is demonstrated. Time characteristics of the response have been studied.

DOI： 10.1088/0268-1242/16/5/304

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Spatial distribution of the cyclotron radiation emitted from nonequilibrium electrons is studied on 1.5 ms-wide Hall bars in the quantized Wall effect (QHE) regime. At low current levels where the two terminal resistance is quantized, the location of the cyclotron emission (CE) is restricted to the electron entry and exit corners formed between the metallic current contacts and the two-dimensional electron gas (2DEG) layer, As current increases, additional CE occurs in the vicinity of the corner of the source contact that is opposite to the electron entry corner. The additional CE is accompanied by a finite voltage drop. The experimental results demonstrate that in sufficiently wide Hall bars the QHE breaks down locally in the vicinity of the source contact before the breakdown develops in the entire 2DEG channel. (C) 2000 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1386-9477(00)00061-8

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

Spatial distribution of the cyclotron radiation emitted from nonequilibrium electrons is studied on 1.5 mm-wide Hall bars in the quantized Hall effect (QHE) regime. At low-current levels whare the two terminal resistance is quantized, the cyclotron emission (CE) is observed at the electron entry and exit corners formed between the metallic current contacts and the two-dimensional electron gas (2DEG) layer. As the current increases, additional CE occurs in the vicinity of the corner of the source contact that is opposite to the electron entry corner. The additional CE is accompanied by a finite voltage drop. The region over which the finite voltage drop takes place is localized to the limited region adjacent to the source contact where the CE is observed, and shows that the QHE breaks down locally in the vicinity of the source contact before the breakdown develops in the entire 2DEG channel. Studies of device-width dependence reveal that this local breakdown of the QHE in the vicinity of the source contact takes place only in sufficiently wide Hall bars (with a width well larger than 200 mu m). All the experimentally observed features are reasonably interpreted by assuming that electron-hole pairs are generated in cascading process due to strong polarization fields formed along the interface between the metallic source contact and the 2DEG.

DOI： 10.1103/PhysRevB.61.2931

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記述言語：日本語   出版者・発行元：日本材料科学会  

CiNii Books

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記述言語：英語   出版者・発行元：AMER PHYSICAL SOC  

Emissions of cyclotron radiation associated with the inter-landau-level transition of nonequilibrium electrons are experimentally studied in quantum-Hall-effect devices. It is confirmed that both the longitudinal resistance and the contact resistance an vanishing when the cyclotron emission (CE) is being observed. For the CE, a critical source-drain voltage V-SD is found to exist at V-SD = h omega(c)/2e, where h omega(c) is the inter-landau-level energy spacing. Spatially resolved measurements reveal that the CE takes place at both of the current entry and exit corners ("hot spots") of the Hall bars, A model of ideal current contacts is discussed. The CE on the source side is interpreted as being due to injection of nonequilibrium electrons from the source contact, and the CE on the drain side as due to an inter-landau-level electron tunneling caused by a steep potential wall formed at the drain contact. [S0163-1829(99)04619-6].

DOI： 10.1103/PhysRevB.59.12537

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記述言語：英語   出版者・発行元：TRANSTEC PUBLICATIONS LTD  

Cyclotron resonance photoconductivity of 2D electrons in GaAs/AlGaAs heterostructure in millimeter and submillimeter wavelength range 130 - 2700 GHz in magnetic fields up to 6 T at T= 4.2 K was investigated. At low frequences the cyclotron resonance is accompanied by Shubnikov-de Haas-like oscillations of the photoconductivity. At higher frequences the response (versus magnetic field) is shown to consist of few lines corresponding to even values of the filling factor around the resonant field. Quantum Hall effect device was demonstrated to be a sensitive tunable narrow band far infrared detector.

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