Peculiarities in the photoelectrical properties of CdS single crystals irradiated with fast-pile neutrons

Results of experiments on the effect of fast-pile-neutron irradiation on the photoelectrical properties of CdS single crystals are discussed. It is shown that the fast neutrons introduce defects into the CdS which give rise to: (i) electron levels at E c -0.44, E c -0.5, E c -0.6 and E c -0.9 eV; (ii) defect clusters where the radius of the effective space-charge region is approximately 300 AA; (iii) a potential barrier at 0.40+or-0.05 eV. It is shown that the level at E c -0.9 eV arises from Frenkel defects in the cadmium sublattice. The decay time tau of the photocurrent after irradiation increases approximately 10 6 times after a neutron dose of 2*10 18 n cm -2 and also increases when the temperature increases, with an activation energy of 0.5 eV. A model is proposed in this paper to explain both the anomalous temperature dependence of tau , and the photoconductivity spectrum.