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Svoboda, P.; Středa, P.; Nachtwei, G.; Jaeger, A.; Cukr, M.; Láznička, M.

doi:10.1103/physrevb.45.8763

Cited by 33 publications

(38 citation statements)

References 12 publications

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“…This asymmetry is moreover strongly dependent on current I, which is illustrated in Fig.1a and Fig.1b for the samples A and B, respectively. The resistivity minimum around ν=2 is shown here in the interval of currents covering the transition from non-local to local resistivity discussed extensively elsewhere [9,10]. While the upper (low-energy) edge of the Shubnikov -deHaas (SdH) peak corresponding to the spin-resolved Landau level 1↑ are shown to depend strongly on the current I , this is not the case for the high-energy edge of the peak 0↓ on the high magnetic field side of the minimum.…”

Section: Methodsmentioning

confidence: 82%

“…This extra contribution can be induced even in the middle of the mobility gap by increasing the current I up to the values where the non-local conduction [9,10] is suppressed and decoupling between the edge and bulk channels has been removed. From the temperature dependence of ̺ xx (B) measured at T ≤ 4.2K with various currents we can conclude, that this is not a simple electron overheating effect.…”

Section: Discussionmentioning

confidence: 99%

“…While the upper (low-energy) edge of the Shubnikov -deHaas (SdH) peak corresponding to the spin-resolved Landau level 1↑ are shown to depend strongly on the current I , this is not the case for the high-energy edge of the peak 0↓ on the high magnetic field side of the minimum. The highest curves correspond to saturation currents where there is a perfect coupling between edge and bulk channels and further increase of I leads to a suppression of the heights of both SdH peaks 1↑ (N=3) and 0↓ (N=2) due to the overheating of the electron gas [10]. An alternative explanation of this asymmetry of the line shapes of the individual spin-resolved subpeaks in ̺ xx (B) for low-indexed Landau levels has been suggested by Haug et al [11].They have shown, that it can reflect an asymmetry in the density of states induced by a particular distribution of the attractive (ionized Si donors in AlGaAs source layer) and repulsive (residual acceptors in GaAs buffer layer) scatterers in samples.…”

Section: Methodsmentioning

confidence: 99%

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Electron conduction within Landau-level tails of medium-mobility GaAs/AlGaAs heterostructures

Svoboda

Nachtwei

Breitlow

et al. 1997

Semicond. Sci. Technol.

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The temperature dependence of both components of the resistivity tensor ̺ xx (T ) and ̺ xy (T ) has been studied at T ≥ 4.2 K within IQHE plateaux around filling factors ν=2 and ν=4 of medium-mobility GaAs/AlGaAs heterostructures. In the middle of the mobility gap standard activated conductivity has been found with activation energies ∆ scaling well with hω c /2 . At filling factors slightly below ν=2 another contribution adds to the activated conductivity at T ≤ 12 K. This additional contribution can be further enhanced at higher mesuring d.c. currents. We suggest, that it arises due to enhanced electric field assisted tunneling across potential barriers separating localized states within the bulk of the sample This effect contributes to the backscattering across the sample leading to an enhanced longitudinal conductivity. The additional contribution to σ xx (T ) can be reasonably well fitted to the formula for the variable range hopping in strong magnetic fields indicating that the hopping can persist even at temperatures well above 4.2K.

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Section: Methodsmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Electron conduction within Landau-level tails of medium-mobility GaAs/AlGaAs heterostructures

Svoboda

Nachtwei

Breitlow

et al. 1997

Semicond. Sci. Technol.

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“…The mobility values are more than four times larger compared with that in previous studies, which indicates the improved quality of h-BN/BP interfaces (7). In spite of using the advanced fabrication technique,  FET and  H saturate at T<20 K, which implies that the disorder scattering dominates over the phonon scattering in this temperature regime, which limits the hole mobility at cryogenic temperature (9). The increase of  H with the carrier density p (Fig.…”

mentioning

confidence: 70%

Achieving Ultrahigh Carrier Mobility in Two-Dimensional Hole Gas of Black Phosphorus

et al. 2016

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Abstract:We demonstrate that a field effect transistor ( Main Text:Few-layer black phosphorus (BP) has received in recent years much attention due to its unique properties making this layered material attractive for technological applications(1-3). This twodimensional crystal has an anisotropic structure (Fig.1a) and is characterized by a BP thickness dependent direct band gap(4). In contrast to graphene, the presence of a band gap in BP permits for a selective depletion of charge carriers by electrostatic gating, which is an essential feature in field effect transistors (FETs). A high charge carrier mobility reaching 1000 cm 2 /Vs at room temperature accentuates this material for applications at room temperature(5). However, the exposure of BP crystals to ambient conditions causes the oxidation of BP and significantly degrades the quality of BP channels. Nevertheless, the encapsulation of BP layers by hexagonal boron nitride (h-BN) sheets in air or in an inert gas environment is found to be very effective for preventing BP oxidation(6-8). Surface impurity effects are largely reduced, and high charge carrier mobility up to several 10 3 cm 2 /Vs has been obtained in BP FETs at cryogenic temperature(6-8). The charge carrier scattering at the impurities encapsulated along with the BP layers hinders further mobility increase. Figure 1a shows Fig.1c). The mobility values are more than four times larger compared with that in previous studies, which indicates the improved quality of h-BN/BP interfaces(7). In spite of using the advanced fabrication technique,  FET and  H saturate at T<20 K, which implies that the disorder scattering dominates over the phonon scattering in this temperature regime, which limits the hole mobility at cryogenic temperature(9). The increase of  H with the carrier density p (Fig. 1c) suggests that the disorder potential is likely created by residual impurities and can be screened by the mobile carriers (7,10,11). The scattering behavior changes at high temperatures (T>100 K).  FET and  H decrease with increasing T and follow the dependence T    , where  =1.9 and 2.0 characterize the dependence for  H and  FET , respectively (black line in Fig. 1c). The large  values imply that the acoustic phonon rather than the optical phonon scattering dominates over the scattering by the residual impurities in this temperature regime. It is very noticeable that the room temperature hole mobility  H = 5200 cm 2 /Vs closely approaches the theoretically predicted hole mobility for a clean five-layer BP sheets, which lies in the range between 4,800 cm 2 V -1 s -1 and 6,400 cm 2 V -1 s -1 (9). The realization 4 of the predicated mobility value, which is solely limited by the phonon scattering at room temperature, is another demonstration of the improved BP heterostructure quality. Quantum Hall Effect (QHE) in BP 2DHGFigure 2a shows Hall resistance R yx and magnetoresistance R xx as a function of the magnetic field, which is measured in a clean heterostructure at the base temperature of the experim...

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“…This is due to the asymmetry in SdH oscillations, which has been explained by an asymmetry in the density of state [10] and also by different equilibration probabilities of the edge and bulk channels at the sample edges. [11].…”

Section: Methodsmentioning

confidence: 95%

Giant magnetopiezoresistance at the localized‐extended electronic state transition in a high‐mobility 2DEG system

Yamaguchi

Miyashita

Hirayama

2006

Phys. Status Solidi (c)

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A high-mobility two-dimensional electron gas system with a Hall-bar geometry was integrated in a micromechanical cantilever to measure the piezoresistance, i.e., the resistance change induced by the deflection of the cantilever in the quantum Hall regime. The piezoresistance was strongly enhanced at the transition between the localized and extended states, and we obtained a piezoresistive gauge factor as large as 25,000. This "giant magnetopiezoresistance" is caused by the strong strain effect on the electronic state transition and the cantilever will lead to highly sensitive force and displacement sensors at low temperature. . This is because the strain modulates the energy band structure of semiconductors via the deformation potential or the piezoelectric field, leading to a large change in the carrier concentration and mobility. PR has long been employed in practical sensors, and it is extremely important in recent micro/nanoelectromechanical systems (MEMS/NEMS), where the mechanical signal is transduced into an electrical signal using it [2][3][4]. Until now, MEMS/NEMS operation has been based on PR as a bulk property, and the transducer efficiency has been simply determined by the geometrical shape of the mechanical structure and the piezoelectric coefficient of the material used.We have proposed the use of quantum low-dimensional structures in order to further enhance the PR of semiconductors [5][6][7][8]: electron interference in quasi one-dimensional electron systems [5,6], energy quantization in two-dimensional electron gas (2DEG) systems under magnetic field [7], and the proximity effect in semiconductor/superconductor junction [8]. The common mechanism leading to increased PR lies in the highly non-linear response of device conductance with respect to the external parameters, such as the magnetic field and bias current. When we choose these parameters in such a way that the conductance is most sensitive to their change, the conductance is also sensitive to the induced strain, leading to large PR.One of the most interesting semiconductor low-dimensional systems providing such large nonlinear response is a quantum Hall system. As a function of magnetic field, the longitudinal resistance drastically changes at the magnetic filed, providing the transition between localized and extended electronic states. We, therefore, expected that the induced strain would also cause an abrupt transition between these two electronic states, leading to an extremely large PR. Here we report measurements of the PR of a GaAs/AlGaAs high-mobility 2DEG system and confirm a drastic increase in PR at the transition between these two states as expected.

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Current-induced coupling of the edge and bulk channels in GaAs/AlxGa1

Cited by 33 publications

References 12 publications

Electron conduction within Landau-level tails of medium-mobility GaAs/AlGaAs heterostructures

Electron conduction within Landau-level tails of medium-mobility GaAs/AlGaAs heterostructures

Achieving Ultrahigh Carrier Mobility in Two-Dimensional Hole Gas of Black Phosphorus

Giant magnetopiezoresistance at the localized‐extended electronic state transition in a high‐mobility 2DEG system

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