Hall effect analysis in irradiated silicon samples with different resistivities

The changes induced by neutron irradiation in n- and p-type silicon samples with starting resistivities from 10 Ω·cm up to 30 KΩ.cm, grown using different techniques, as Float-Zone (FZ), Czochralski (CZ) and epitaxial, have been analyzed by Van der Pauw and Hall effect measurements. Increasing the fluence, each set of samples evolves toward a quasi-intrinsic p-type material. This behavior has been explained in the frame of a two-level model, that considers the introduction during irradiation of mainly two defects, a deep acceptor, probably divacancy related, placed in the upper half of the forbidden gap, and a deep donor one, which is supposed to be related to the C_iO_i complex. This simple model explains quantitatively the data on resistivity and Hall coefficient of each set of samples up to the fluence of ≈10¹⁴ n/cm²