Device parameter optimization of strained Si channel SiGe/Si n-MODFET's using a one-dimensional charge control model

We have simulated the strained Si channel SiGe n-MODFET structure using a one-dimensional (1-D) self-consistent Schroedinger-Poisson charge control model. The quantum confinement effect has been investigated and key transistor parameters have been optimized for maximum f/sub T/. It has been found that the doping concentration into the donor layer and the Ge mole fraction of the SiGe layers should be as high as possible, provided that the doping diffusion and the avalanche breakdown are under control and the crystalline quality of the epilayers is not significantly degraded. The optimum channel thickness was found to be between 5 and 7.5 nm. In addition, it has been shown that the thickness of the donor layer should be used for threshold voltage adjustment rather than for f/sub T/ improvement.

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