If we dope the silicon with phosphorous, we can create an n$-$type semi$-$conductor. Let$$s replace every $10-$

millionth silicon atom with an atom of phosphorous. What will be the concentration $($atoms$/$m$3)$ of phosphorus

atoms? Since each phosphorus atom has an additional electron available for conduction, this will also be the

concentration of electrons available for conduction. Note that this is many times larger than the concentration

of charge carriers due to the silicon alone from part b$.$ Thus the conduction in the doped silicon will be due

almost entirely to the electrons added by the doping process, and the intrinsic charge carriers can be neglected.

Using this concentration of electrons, and the same electron mobility, calculate the conductivity and resistivity

of the doped n$-$type silicon.