Authors: N. Cavassilas and J-L Autran
Affilation: CNRS, France
Pages: 600 - 603
Keywords: strain, band-structure, strained Si, SiGe, k.p theory, Schödinger and Poisson equations, capacitance-voltage (C-V) characteristic
We present theoretical investigation of mechanical strain-induced effects in metal-oxide-semiconductor (MOS) structures from an electrical point-of-view. In this work, we start by calculating the strained semiconductor band-structure using a k.p approach over the complete Brillouin zone for the conduction and valence bands. The present method has been applied to silicon strained on an unstrained  Si1-xGex buffer surface. The resulting carrier effective masses, energy split and energy bandgap deduced from the strained si band-structure have been introduced in a one-dimensional solver of the Schrödinger and Poisson equations. Self-consistent calculation of the capacitance-voltage (C-V) curves has been then performed for n+-poly/SiO2/p-Si/Si1-xGex structures with Ge content x ranging from 0 up to 0.5. Our results highlight a strain dependence of the threshold voltage of the MOS structure due to the energy bandgap reduction and a non-linear strain effect in accumulation due to the degeneracy in the valence band.