An improved Monte Carlo model for ionized impurity scattering is developed and applied to transport problems in Si and the Si$\sb{1-x}$Ge$\sb x$ alloy system. The model includes scattering cross sections derived from phase-shift analysis, implementation of the Friedel Sum Rule, and a simple phenomological model for multiple-potential scattering. Using a single adjustable parameter, majority and minority electron mobilities are calculated for Si and fit to experimental data. Experimental results for Si of $\mu\sb n(N\sb A)/\mu\sb n(N\sb D) \approx$ 2 at 300 K are reproduced and a value of 3 $< \mu\sb n(N\sb A)/\mu\sb n(N\sb D) <$ 4 is predicted at 77K. Low-field mobilities are then calculated for both strained and unstrained Si$\sb{1-x}$Ge$\sb x$ over wide ranges of doping, Ge mole fraction, and electric field, at 300K and 77K. A significant improvement in mobility (up to 50%) is observed for transport perpendicular to the growth plane in strained Si$\sb{1-x}$Ge$\sb x$, especially at 77K. High field MC simulations show that some strained mobility enhancement remains even at an electric field of 100 kV/cm. The improved model is then used in both DDE and Monte Carlo simulations at 300K and 77K of two strained-layer n-p-n Si$\sb{1-x}$Ge$\sb x$ HBTs with basewidths of 1000 A and 650 A and maximum Ge contents of 15% and 10% respectively. We find that as a result of improved mobility in the base and collector and velocity overshoot in the high field region, $h\sb{fe}$ and $f\sb T$ are improved significantly for the strained 650 A basewidth HBT as compared to a similar unstrained structure, especially at 77K.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.