On Surface Roughness Scattering-Limited Mobilities of Electrons and Holes in Biaxially Tensile-Strained Si MOSFETs

In this letter, we examine the impact of biaxial tensile strain on the surface roughness scattering-limited mobility (??_sr) of electrons and holes, experimentally. It is found that tensile strain monotonically enhances electron ??_sr with the increase in the amount of strain but does not enhance hole ??_sr even when the strain is quite high (in the Si_1- xGex relaxed layers with 40% Ge content). This different strain dependence of electron and hole ??_sr can be explained by a combination of a slight reduction in the roughness height (??) of the Si/SiO₂ interfaces and a decrease in the correlation length (??), induced by tensile strain. The strain-induced ?? reduction is confirmed by direct transmission electron microscopy measurements for the first time.