Czochralski grown n-type Si and Ge samples with carrier concentrations between 6x1014 and 3x1015cm-3 were irradiated with fast neutrons to a dose of 2.4x1012cm-2. Electrically active defects have been studied by means of conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS. The evolution of these defects has been studied using 30-min isochronal annealing in the temperature range 100-300 C.
The neutron irradiation resulted in the appearance of peaks related to electron deep level traps in the DLTS spectra in all the materials. The dominant defect immediately after irradiation was the E centre in Ge, but in Si peaks related to the divacancy and small vacancy clusters dominated. One of the possible reasons for this is the charge state of the single vacancy during irradiation. In silicon it is anticipated the vacancy will be neutral whereas it will be in the negatively charged in Ge. In consequence the formation of multi-vacancy complexes is suppressed in the Ge rich materials. Annealing studies revealed different defect reaction pathways in the different materials and proposals are made in relation to their identification as interstitial and vacancy complexes.