Imaging of edge channels in the integer quantum Hall regime by the lateral photoelectric effect

Haren, van Rjf Richard; Blom, Fap Frans; Lange, de Wgj

doi:10.1016/0039-6028(96)00399-8

Surface Science

1996

DOI: 10.1016/0039-6028(96)00399-8

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Imaging of edge channels in the integer quantum Hall regime by the lateral photoelectric effect

van Rjf Richard Haren

Fap Frans Blom

de Wgj Lange

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Cited by 2 publications

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“…6,7 Meanwhile, SPVM experiments have focused primarily on the quantum Hall regime to visualise edge channel transport at the sample boundaries. 8,9 Recently, SPVM has been used to image ballistic photocurrents, 10 spin-dependent transverse photovoltages, 11 and metal-semiconductor interface effects 12,13 in GaAs-based microstructures. Meanwhile, InSb 2DEG structures are particularly well suited to sensing applications due to the high RT electron mobility 14,15 of l e < 60 000 cm 2 /V s, exceeded only by that in suspended/encapsulated graphene.…”

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confidence: 99%

Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

Gilbertson

Sadeghi

Panchal

et al. 2015

Applied Physics Letters

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Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

Gilbertson

Sadeghi

Panchal

et al. 2015

Applied Physics Letters

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“…Previously, a similar approach has been used to investigate contact-induced band bending [16][17][18][19] and the photo-thermoelectric effect 20 in graphene at B = 0, as well as the electrostatics of the QHE in conventional semiconductor devices [21][22][23] . We observe that the gate-voltagedependent photocurrent at fixed locations is oscillatory, with polarity determined by the direction of the magnetic field (Fig.…”

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confidence: 99%

Visualization of charge transport through Landau levels in graphene

Nazin

Zhang

et al. 2010

Nature Phys

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Band bending and the associated spatially inhomogeneous population of Landau levels play a central role in the physics of the quantum Hall effect (QHE) by constraining the pathways for charge-carrier transport and scattering 1 . Recent progress in understanding such effects in low-dimensional carrier gases in conventional semiconductors has been achieved by realspace mapping using local probes 2,3 . Here, we use spatially resolved photocurrent measurements in the QHE regime to study the correlation between the distribution of Landau levels and the macroscopic transport characteristics in graphene. Spatial maps show that the net photocurrent is determined by hot carriers transported to the periphery of the graphene channel, where QHE edge states provide efficient pathways for their extraction to the contacts. The photocurrent is sensitive to the local filling factor, which allows us to reconstruct the local charge density in the entire conducting channel of a graphene device.Since the demonstration of the unusual half-integer QHE in graphene 4,5 , many related QHE experiments have been interpreted within the framework of edge-state transport [6][7][8] , that is, the backscattering-free flow of charge through edge states 9 bounded by insulating barriers with incompressible electron densities 10 . Although compressible and incompressible electron densities have recently been observed in graphene 11 , their role in shaping the QHE in graphene remains to be explained. Spatially inhomogeneous charge distributions owing to adsorbate-induced surface doping 12 are expected to be particularly pronounced in graphene and could cause deviations from pure edge-state transport. Here, we use scanning photocurrent microscopy to explore these effects by mapping carrier propagation through graphene Landau levels in the QHE regime.The experiments were carried out on two-terminal monolayer graphene field-effect devices at 4.2 K and in magnetic fields B up to ±9 T (Fig. 1a,b). In these conditions, the conductance of our devices (Fig. 1c) shows series of local extrema 6,8,11,13,14 associated with individual Landau levels 13,15 , with maxima predicted to occur at quantized Hall conductances of 2, 4, 6, 10 and 14 e 2 /h (refs 13,15). The observed maxima are higher owing to an inhomogeneous filling-factor distribution across the device, as shown below.Photocurrent maps were obtained by scanning a focused laser across the graphene channel, and recording the two-terminal photocurrent signal as a function of beam position. Previously, a similar approach has been used to investigate contact-induced band bending [16][17][18][19] and the photo-thermoelectric effect 20 in graphene at B = 0, as well as the electrostatics of the QHE in conventional semiconductor devices [21][22][23] . We observe that the gate-voltagedependent photocurrent at fixed locations is oscillatory, with polarity determined by the direction of the magnetic field (Fig. 1d). Such local oscillations are due to a recurring global photocurrent distribution across the device, sy...

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Imaging of edge channels in the integer quantum Hall regime by the lateral photoelectric effect

Cited by 2 publications

References 12 publications

Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

Multifunctional semiconductor micro-Hall devices for magnetic, electric, and photo-detection

Visualization of charge transport through Landau levels in graphene

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