Monte Carlo calculation of strained and unstrained electron mobilities in Si1-xGex using an improved ionized‐impurity model

An improved Monte Carlo (MC) model for ionized impurity scattering developed in a previous work [L. E. Kay and T.‐W. Tang, J. Appl. Phys. 70 1475 (1991)] is used to perform a comprehensive study of majority‐ and minority‐electron mobilities in the Si1-xGex material system for both strained and unstrained cases. This investigation includes calculation of low‐field mobilities for wide ranges of doping and Ge mole fraction at both 300 and 77 K as well as high‐field studies. A significant improvement in mobility (up to 50%) is observed for transport perpendicular to the growth plane in strained Si1-xGex as compared to the unstrained case. The magnitude of the improvement is dependent on doping (both concentration and type) and germanium content, and is somewhat larger at 77 K. High‐field MC simulations show that some strained‐mobility enhancement remains even at an electric field of 100 kV/cm. These studies also suggest there is a temperature‐dependent Ge content for which mobility is maximized at higher dopings.