[填空题]
Suppose that a silicon semiconductor is doped d qufx;r )o05w) x2ldtwith phosphd/: ax5 qwu3sworus so that one silicon a s3:wxwuqa/ d5tom in $ 10^6 $ is replaced by a phosphorus atom. Assuming that the "extra" electron in every phosphorus atom is donated to the conduction band, by what factor is the density of conduction electrons increased? The density of silicon is $ 2330\ \text{kg/m}^3 $, and the density of conduction electrons in pure silicon is about $ 10^{16}\ \text{m}^{-3} $ at room temperature. $\frac{N_{doping}}{N_{Si}} = $ $ \times 10^6$
