The creation of highly conductive ultrashallow-doped regions in strained Si is a key requirement for future Si based devices. It is shown that in the presence of tensile strain, Sb becomes a contender to replace As in strain-engineered CMOS devices due to advantages in sheet resistance. While strain reduces resistance for both As and Sb; a result of enhanced electron mobility, the reduction is significantly larger for Sb due to an increase in donor activation. Differential Hall measurements suggest this is a consequence of a strain-induced Sb solubility enhancement following solid-phase epitaxial regrowth, increasing Sb solubility in Si to levels approaching 10(21) cm(-3). Experiments highlight the importance of maintaining substrate strain during thermal annealing to maintain this high Sb activation. (c) 2008 Elsevier B.V. All rights reserved.