Effects of Screening and Neutral Impurity on Mobility in Silicon Inversion Layers under Uniaxial Stress

Abstract

The mobility in a two-subband system realized in an n-channel inversion layer at the Si(100)/SiO₂ interface under the stress along the [001] direction is calculated at zero temperature. In addition to the two mechanisms—charged impurity scattering and surface roughness scattering, scattering by a neutral impurity composed of a positively charged impurity at the interface and an electron trapped by it is introduced as the third mechnaism. The wave function of the trapped electron is determined variationally and is extended rather widely in the semiconductor to make the scattering cross section large. The screening of electrons in the inversion layer is evaluated in the RPA and the Born approximation is employed to calculate the relaxation time. The combination of these three mechanisms explains the experiment well.