Shift of the Fermi level and inversion of the type of conduction due to irradiation of n-type Si

Crystals of n-type Si grown by the zone melting in vacuum exhibit n-p inversion of the type conduction and a shift of the Fermi level EF to the lower half of the band gap and the position EF = Ev + 0.39 eV as a result of irradiation with high-energy particles. This investigation was carried out in order to determine the nature of structure defects responsible for such a shift of EF, since the published data on this topic were ambiguous and contradictory. The authors investigated phosphorus-doped crystals of n-type Si grown by the zone melting method in which the concentrations of residual impurities (oxygen and carbon) deduced from an activation analysis did not exceed 2·1016 cm-3. The experimental results were in the form of the temperature dependences (T = 20-400 K) of the Hall coefficient measured at different stages of irradiation and annealing and analyzed on the basis of the electrical neutrality equation