Deep-level transient spectroscopy studies of U-irradiated silicon

N-type, float zone silicon samples have been irradiated at GSI Darmstadt by 3.6 GeV U ions presenting a high electronic stopping power of 28 MeV/μm. The irradiation has been performed at room temperature so that no recovering stage has occurred before DLTS measurements. To this end, samples irradiated at low fluence (2x1010 U/cm2) have been selected. Three resolved peaks corresponding to electron traps appear on the spectra. They can be associated with the vacancy-oxygen (A center), the divacancy and the phosphorus-vacancy (E center). No extented defect has been detected. The bulk concentration of these traps has been determined using the DDLTS method. From these values we have evaluated the total production rate of primary defects (vacancy) and normalized it by the number of displaced atoms per atom resulting from nuclear (elastic) collisions. A comparison with electron irradiations shows that the electronic stopping power is inefficient for defect creation in n-type silicon at room temperature. (orig.)