An N-type sample of silicon has uniform density (Nd = 1019/cm–3 ) of arsenic, and a P-type silicon sample has a uniform density (Na = 1015 /cm–3 ) of boron. For each sample, determine the following: (a) The temperature at which the intrinsic concentration ni exceeds the impurity density by factor of 10. (b) The equilibrium minority-carrier concentrations at 300 K. Assume full ionization of impurities. (c) The Fermi level relative to the valence–band edge Ev in each material at 300 K. (d) The electron and hole concentrations and the Fermi level if both types of impurities are present in the same sample