Chapter

Metal–Insulator Transitions in Two-dimensional Electron Systems

S.V. Kravchenko

in Conductor-Insulator Quantum Phase Transitions

Published in print June 2012 | ISBN: 9780199592593
Published online September 2012 | e-ISBN: 9780191741050 | DOI: http://dx.doi.org/10.1093/acprof:oso/9780199592593.003.0002
Metal–Insulator Transitions in Two-dimensional Electron Systems

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This chapter presents a summary of the experimental results on large r s 2D electron and hole gases (2DEGs and 2DHGs) in clean semiconductor devices. In particular, it focuses on experiments on the following systems: silicon metal-oxide-semiconductor field-effect transistors (MOSFETs), p-GaAs heterojunctions and quantum wells, n-GaAs heterojunctions, p- and n-SiGe quantum wells, and AlAs quantum wells. The typical values of r s are ~ 10-40, depending on the device. The high r s regime is easier to reach in Si MOSFETs than the much cleaner n-GaAs-based devices, due to relatively high effective mass, lower average dielectric constant, and the existence of two degenerate valleys in the spectrum, which further increase r s by a factor of 2. As a result, to reach the same interaction strengths, electron densities two orders of magnitude lower are needed in n-GaAs heterojunctions compared to those in Si MOSFETs. The great similarities in the data obtained on different types of 2D system imply that the observed behaviours are robust, universal, and largely independent of details, in spite of the fact that in various 2D structures there are significant differences between the electronic spectrum and the nature of the disorder potential.

Keywords: electron systems; semiconductors; MOSFETs; p-GaAs heterojunctions; n-GaAs heterojunctions; quantum wells; electron density; transport properties; magnetic properties

Chapter.  6849 words.  Illustrated.

Subjects: Mathematical and Statistical Physics

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