2.3.1 Strained-Silicon Devices

The mobility of carriers in silicon is enhanced if biaxial tensile strain is applied [25], because under tensile strain in (001) silicon, the fourfold-degenerate conduction band ellipsoids with the higher effective mass are lifted. Thus, more carriers remain in the two-fold degenerate ellipsoids with lower effective mass. Additionally, inter-valley scattering is reduced. Strained silicon channels can be realized by growing a thin layer of silicon on a material with a slightly larger lattice constant, such as silicon-germanium. The silicon layer must be thin enough to prevent relaxation and strain relief.

A. Gehring: Simulation of Tunneling in Semiconductor Devices