Subsurface Charge Accumulation imaging of the quantum Hall liquid

We describe results obtained by a novel scanning technique, called Subsurface Charge Accumulation (SCA) Imaging, that enables the direct imaging of electronic systems buried inside semiconductor materials. Using SCA Imaging, we image and measure properties of a two-dimensional electron system (2DES) in a GaAs/AlGaAs heterostructure, in the regime of the integer quantum Hall effect. We observe general charging features in a plain 2DES near quantum Hall integer filling factors. We proceed by imaging low compressibility strips in the presence of an artificially created density gradient in the 2DES. We study them in detail at Landau level filling factors v = 2, 4. The strips appear significantly wider than predicted by theory and we account for the discrepancy by presenting a model that considers the disorder-induced nonzero density of states in the cyclotron gap. We also measure the charging properties of incompressible strips that form parallel to the edges of a metal gate deposited on the surface of our sample. An RC model considering charging of the 2DES across the strip, closely fits the data. This allows us to determine the longitudinal resistivity of the incompressible part of the edge state that runs parallel to the gate, for a range of filling factors. Surprisingly, the strip becomes more resistive in regions of high electronic density gradient, where its width is expected to decrease. By sensing charge from the motion of single electrons inside the 2DES we produce a topographic map of the random potential inside the integer quantum Hall liquid.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Glicofridis, Paul Ioannis, 1973-

Advisor dc:contributor.advisor

• Raymond C. Ashoori.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29894

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29894