Temperature and interface-roughness dependence of the electron mobility in high-mobility Si(100) inversion layers below 4.2 K

An analysis is made of the mechanisms limiting the mobility in Si(100) inversion layers that have peak mobilities (at 4.2 K) ranging from 2.0 to 2.5 ${\mathrm{m}}^2$/V s. At high electron density, this work focuses on the statistical properties of the Si-${\mathrm{SiO}}_2$ interface roughness, which provides the dominant scattering mechanism in this regime. We find that the agreement between theory and experiment is considerably improved if the roughness is described by an exponential instead of the usual Gaussian correlation. This supports a recently developed model of the microstructure of the interface which is based on high-resolution transmission electron microscopy data. At low electron density, Coulomb scattering and temperature-dependent screening are taken into account to describe the data. The discrepancies that remain cannot entirely be lifted by the inclusion of multiple-scattering effects. On the other hand, band tailing describes the mobility well over the entire range of electron density considered. The observed temperature dependence of mobility is in excellent agreement with theory.