Neutron irradiation influence on mobility and compensation of dark conductivity in silicon

The electrical properties of the neutron irradiated Si were analysed by means of the Hall effect and magnetoresistance temperature dependence. It was demonstrated that the electron mobility decreased with increasing the neutron fluence in a wide fluence range, and the microinhomogeneities in samples caused differences between the mobility values from the measured Hall and magnetoresistance effects. Exploiting the magnetoresistance mobility temperature dependence, the free carrier concentration dependence on temperature was analysed. It was found that the neutron irradiation introduced deep levels in the upper part of the bandgap, but their contribution decreased with increasing the neutron fluence – that is explained by more effective generation of acceptor type levels in the middle or lower part of the bandgap. The activation energy of the free carrier concentration did not follow the homogeneous semiconductor model, so the dark conductivity origin, that is related to the modified cluster model and cluster environment, was proposed.