Physicsbased Singlepiece
Charge Model for StrainedSi MOSFETs
Karthik Chandrasekaran, Xing Zhou, Senior Member, IEEE,
Siau Ben Chiah, Wangzuo Shangguan, and Guan Huei See
IEEE Transactions on Electron Devices,
Vol. 52, No. 7, pp. 15551562, July 2005
(Manuscript received December 20, 2004; revised
April 6, 2005.)
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Abstract
A physicsbased singlepiece charge model for strainedsilicon (sSi)
MOSFETs from accumulation to stronginversion regions is presented.
The model is formulated from regional solutions of the wellknown Pao–Sah
equation and unified with interpolation functions while keeping the physics
in the derived flatband voltages that depend on the device material and
structural parameters, such as band gaps, conduction and valence band offsets,
Ge mole fraction, layer thickness, and doping. The model is validated
by comparison with numerical devices for a wide range of Ge mole fractions
and s Si layer thicknesses. It is shown that the model accurately
describes the physical behavior of the surface potentials, terminal charges
and capacitances, especially charge accumulation/depletion at the s Si/SiGe
interface that gives rise to the observed "plateau" in the capacitancevoltage
characteristics.
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