Radiation hardness of silicon—a challenge for defect engineering

Thermally stimulated current measurements of silicon particle detectors have been performed for defect characterization after high levels of $\gamma$- and proton-irradiation. Two defects closely correlated with the detector performance were monitored: a deep acceptor (I) and a bistable donor (BD). In oxygen rich silicon the deep acceptor is largely suppressed while the BD generation is strongly enhanced. The influence of the starting material (standard float zone (FZ), oxygen enriched FZ, Cz, epitaxial silicon) on the formation of these two defects is discussed. Identification of the I-defect with the V$_2$O complex, and of BD with the thermal double donor TDD2 is suggested.