P-type doping

In a pure silicon semiconductor the excitation of electrons, that is allowing electrons jump out of covalent bonds will require an energy of 1.1 eV. This is why a silicon crystal is a poor conductor at room temperature. In order to increase the electric conductivity of silicon crystals, you have to increase the amount of free charged particles. This can be best achieved by doping the semiconductor crystal, so that a part of the tetravalent Si atoms in the crystal are replaced by for instance trivalent boron atoms (B).

N-type doping

In a pure silicon semiconductor excitation of electrons, that is allowing electrons jump out of covalent bonds will require an energy of 1.1 eV. This is why a silicon crystal is a poor conductor at room temperature. In order to increase the electric conductivity of silicon crystals, you have to increase the amount of free charged particles. This can be best achieved by doping the semiconductor crystal,so that a part of the tetravalent Si atoms in the crystal are replaced by for instance pentavalent phosphorus atoms (P).