The second species are implanted into substantially the same regions as the first species using an ion implantation process, thereby forming a doped region 221 in the exposed source/drain regions 292, as shown in FIG. 6. The doped regions 221 may overlap the amorphous regions 219, meaning the second species may be randomly distributed in the amorphous regions 219 containing the first species. In some embodiments, the dopant implantation process may create a distribution of the second species within the amorphous regions 219, with the peak or highest concentration of second species being near the top surface 215 of the source/drain regions 292, and lower concentration deeper into the amorphous regions 219 (or source/drain regions 292). In an embodiment, the second species has a peak concentration equal to or greater than about 1×10²¹ A/cm³ at a vertical depth in a range between about 2 nm to about 4 nm, and the concentration of the second species decreases in the source/drain region from the peak concentration of the second species in a direction away from the top surface 215 of the source/drain region. The depth of the doped regions 221 can be controlled by changing the implantation energy, substrate temperature, and/or the tilt angle. While the amorphous regions 219 may generally have a greater, deeper distribution within the source/drain regions 292 than that of the doped regions 221, in some embodiments the doped regions 221 may extend over the boundary of the amorphous regions 219 to a region between the boundary of the amorphous region 219 and the boundary of the first region 213. In some embodiments, the doped regions 221 may further extend into the second region 217. In most cases, the diffusion of the dopants can be further increased by the subsequent annealing processes.