Semiconductor nanowires (NWs) have been widely investigated over the last few decades because of their unique quantum-confined physical properties which enable novel applications and their potential to play a key role in future electronics. The physical properties of binary-alloy Si(1-x)Gex NWs can be altered both by doping and by changing their chemical alloy composition. The simultaneous control of both parameters is therefore essential, although not straightforward, for the complete utilization of Si(1-x)Ge x NWs. While the influence of several growth parameters on the composition of Si(1-x)Gex NW alloys was recently explored, the interplay of simultaneously controlling both dopant concentration and alloy composition has not yet been investigated. This study shows that the introduction of either boron or phosphorus as dopants, by the use of diborane (B2H6) or phosphine (PH3) during the growth of the Si(1-x)Gex NW, has a significant influence on the chemical alloy composition of the NWs produced. This leads to unexpected changes in its physical properties. Therefore, the tailoring of these properties of the NW during its growth requires a complete understanding of the interplay between the doping type and level and the chemical composition. Other aspects of the growth and properties of the Si(1-x)Gex NW, such as morphology, growth rate, growth yield, and electrical properties, were studied as well.