Attention was focused upon the investigation of radiation-induced defects responsible for the degradation of silicon detector performance. Comparative studies of the defects induced by irradiation with 60Co-γ rays, 6 and 15MeV electrons, 23GeV protons and reactor neutrons revealed the existence of point defects and cluster-related centers having a strong impact on damage properties of Si diodes. The detailed relation between the “microscopic” reasons as based on defect analysis and their “macroscopic” consequences for detector performance was presented. In particular, it was shown that the changes in the Si device properties (depletion voltage and leakage current) after exposure to high levels of 60Co-γ doses could be completely understood by the microscopically investigated formation of two point defects, a deep acceptor and a shallow donor, both depending strongly on the oxygen concentration in the silicon bulk. Specific for hadron irradiation were the annealing effects which decreased (increased) the originally observed damage effects as seen by the changes of the depletion voltage and these effects were known as “beneficial” and “reverse” annealing, respectively. A group of three cluster-related defects, revealed as deep hole traps, proved to be responsible specifically for the reverse annealing. Their formation was not affected by the oxygen content or silicon growth procedure suggesting that they were complexes of multi-vacancies located inside extended disordered regions.

Radiation-Induced Point- and Cluster-Related Defects with Strong Impact on Damage Properties of Silicon Detectors. I.Pintilie, G.Lindstroem, A.Junkes, E.Fretwurst: Nuclear Instruments and Methods in Physics Research A, 2009, 611[1], 52-68