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-

x
Ge
x
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/SiO
₂
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.