Zero-bias thermally stimulated currents (ZB-TSC) spectroscopy of deep traps in irradiated silicon particle detectors

A zero-bias thermally stimulated currents (ZB-TSC) study has been carried out on n-type magnetic Czochralski silicon diodes irradiated with neutrons in the (1 MeV equivalent neutron) fluence range of Φ=1013–1015 neq/cm2. In standard TSC, deep-level emissions can be analyzed as long as they are clearly distinguishable from the background current, which increases exponentially during the heating scan. On the contrary, in ZB-TSC this problem is overcome because background current is negligible. As an example, at Φ=1015 neq/cm2, we found a maximal temperature of investigation with standard TSC close to ∼150 K, while with ZB-TSC this value is higher than 250 K. Moreover, ZB-TSC can be used to evidence the complex structured electric field profile due to charged defects in the irradiated material. Therefore, ZB-TSC results in a very useful tool to characterize radiation damage in heavily irradiated silicon detectors, permitting both to explore the whole band gap and to obtain information about the residual electric field profile. Our ZB-TSC measurements showed the presence of radiation-induced deep levels in the range 0.37–0.51 eV, while no deeper levels were found.