Strain-Induced, Off-Diagonal, Same-Atom Parameters in Empirical Tight-Binding Theory Suitable for  Uniaxial Strain Applied to a Silicon Parametrization
Date of this Version3-5-2010
Phys. Rev. B 81, 125202 (2010)
This document has been peer-reviewed.
State-of-the-art transistors achieve their improved performance through strain engineering. The somewhat unusual uniaxial  strain is of particular importance as it provides a significant mobility increase for electrons. Empirical tight binding has shown tremendous benefits in modeling realistically large structures including standard strain conditions, but often fails to predict the correct uniaxial  strain behavior because most treatments neglect the same-atom different-orbital matrix elements induced by this strain. Two separate mechanisms are responsible for these conditions: Loumlwdin orbital changes and displacement of nearest-neighbor potentials. We present a model which separately includes both mechanisms via parameters whose range of validity can be independently determined. Using this method we optimize a set of strain parameters for Si. The combination of both effects is able to reproduce the Si X-z-valley transverse mass splitting under uniaxial  strain. We then use this model to calculate the drain current of a strained double-gate, ultrathin-body metal-oxide-semiconductor field-effect transistor, finding experimentally plausible results.
Engineering | Nanoscience and Nanotechnology