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

Studies of various experimental groups that explore the properties of a two-dimensional electron gas in silicon semiconductor systems ((100) Si-MOSFET 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 region 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.