Two-dimensional system of strongly interacting electrons in silicon (100) structures

TL;DR

This paper critically analyzes experimental studies of two-dimensional electron gases in silicon structures near the metal-insulator transition, highlighting common findings about electron effective mass and phase properties.

Contribution

It provides a comprehensive comparison of experimental results in silicon-based 2D electron systems, emphasizing the behavior of effective mass and localization near the transition.

Findings

Electron effective mass increases as electron density decreases.

In Si-MOSFETs, the effective mass tends to diverge at low densities.

In SiGe/Si/SiGe quantum wells, the effective mass saturates at low densities.

Abstract

Studies of different experimental groups that explore the properties of a two-dimensional electron gas in silicon semiconductor systems ((100) Si metal-oxide-semiconductor field-effect transistors (MOSFETs) and (100) SiGe/Si/SiGe quantum wells) in the vicinity of the metal-insulator transition are described and critically analyzed. Results are identified that are common to all research: (i) the effective mass of electrons measured at the Fermi level in the metallic regime increases as the electron density decreases and, if extrapolated, tends to diverge; (ii) the behavior of the energy-averaged mass in the metallic region is quite different in the two systems: in Si-MOSFETs, it also exhibits a tendency to diverge, while in the SiGe/Si/SiGe quantum wells it saturates in the limit of low electron densities; (iii) there is a small number (depending on the sample quality) of localized electrons in the metallic phase; (iv) the properties that the electron system exhibits in the insulating phase in the vicinity of the metal-insulator transition are typical of amorphous media with a strong coupling between particles.