Sample Problem 41.06 Doping silicon with phosphorus
The number density n_0 of conduction electrons in pure silicon at room temperature is about 〖10〗^16 m^(-3). Assume that,by doping the silicon lattice with phosphorus, we want to increase this number by a factor of a million (〖10〗^6). What fraction of silicon atoms must we replace with phosphorus atoms? (Recall that at room temperature, thermal agitation is so effective that essentially every phosphorus atom donates its “extra” electron to the conduction band.) Number of phosphorus atoms: Because each phosphorus
atom contributes one conduction electron and because we want the total number density of conduction electrons to be 106n0, the number density of phosphorus atoms nP must be given by