Detection of the photopopulation and photoionisation of intrinsic point defects in irradiated silicon by IR absorption

The dependence of the intensity of the 0.343 eV (3.62 μm) band as a function of the photon energy of a monochromatic pumping beam perpendicular to the sample beam has been investigated in n- and p-type Si irradiated with neutrons at fluences of 5.7 x 1015 and 1 x 1017 cm-2. From the photoionisation threshold, it is found that the ground state of the band is at Esub(c)-0.34 eV, whereas two levels (at Esub(c)-0.3 eV and Esub(c)-0.5 eV) are clearly involved in the photopopulation increase. These results, as well as the simultaneous observation of the donor spectrum in the n-type sample with a low neutron dose, are not inconsistent with the behaviour of a singly charged negative divacancy, which has been studied extensively by EPR techniques. (author)