Comparison of the radiation hardness of Magnetic Czochralski and Epitaxial silicon substrates after 26Â MeV proton and reactor neutron irradiation

We report on the processing and characterization of microstrip sensors and pad detectors produced on n- and p-type Magnetic Czochralski (MCz), Epitaxial (EPI) and Float Zone (FZ) silicon within the SMART project to develop radiation-hard silicon position sensitive detectors for future colliders. Each wafer contains 10 microstrip sensors with different geometries, several diodes and test structures. The isolation in the strip detectors produced on p-type material has been achieved by means of a uniform p-spray implantation, with doping of 3×1012 cm−2 (low-dose p-spray) and 5×1012 cm−2 (high-dose p-spray). The samples have undergone irradiations with 26 MeV protons and reactor neutrons up to ∼1016 cm−2 1 MeV equivalent neutrons (neq/cm2), and have been completely characterized before and after irradiation in terms of leakage current, depletion voltage and breakdown voltage. The current damage parameter α has been determined for all substrates. MCz diodes show less pronounced dependence of effective doping concentration Neff on the fluence when compared to standard FZ silicon, giving results comparable to diffusion oxygenated FZ devices for all irradiation sources. The observed increase of Neff with fluence can be interpreted in EPI material as a net donor introduction process, overcompensating the usual acceptor introduction process. This effect is stronger for 26 MeV proton irradiation than for neutron irradiation.