28
Strain-Engineered MOSFETs
importance: in-plane biaxial and channel direction uniaxial stress on (001)
and (110) surface-oriented p-MOSFETs with <110> and <111> channels. The
hole mobility vs. uniaxial compressive stress for Ge is shown in Figure 2.8
for (001)-oriented Ge. For (001)-oriented devices, both Si and Ge show large
enhancement. One difference between the two curves is that the mobility
enhancement for Si saturates at about 3 GPa, but it does not saturate until
6 GPa of stress is applied to Ge.
FIGURE 2.7
Germanium hole mobility vs. effective electric field. (After Sun, G., Strain Effects on Hole
Mobility of Silicon and Germanium p-Type Metal-Oxide-Semiconductor Field-EffectTransistors, PhD thesis, University of Florida, 2007.)
FIGURE 2.8
Germanium and silicon hole mobility on (001)-oriented device under uniaxial compressive
stress where the inversion hole concentration is 1 ´ 10 13 /cm 2 . (After Sun, G., Strain Effects on
Hole Mobility of Silicon and Germanium p-Type Metal-Oxide-Semiconductor Field-EffectTransistors, PhD thesis, University of Florida, 2007.)