Determine the required donor impurity concentration to obtain a specified Fermi energy.
Silicon at T=300 \mathrm{~K} contains an acceptor impurity concentration of N_{a}=10^{16} \mathrm{~cm}^{-3}. Determine the concentration of donor impurity atoms that must be added so that the silicon is \mathrm{n} type and the Fermi energy is 0.20 \mathrm{eV} below the conduction-band edge.