# Selenium (Se) is a group VI element (i.e. two columns to the right of Silicon on the periodic table). An extrinsic semiconductor is produced by doping Silicon (Si) with 1020 Selenium atoms per m3. Assuming saturation, calculate the conductivity of the extrinsic semiconductor.

Note: Assume that the mobility of holes is equal to $= 0.05\; m^2/(V.s)$ and that the mobility of electrons is equal to $= 0.14 \;m^2/(Vs)$

Since Selenium is two columns to the right of Silicon, we know that it must be a n-type Extrinsic Semiconductor.
Each atom of Selenium donates two electrons. Therefore, the number of atoms per cubic meter must be multiplied by two to get the number of donated electrons.
$p = 2 \times 10^{20} \text{atomes}\;m^{-3},$
$\sigma = 2 \; p \; e \; \mu_h = $$2 \times 10^{20} \times e \times 0.14 =$$ 4.48\; (\Omega \; m)^{-1}$