Investigation on the improved radiation hardness of silicon detectors withhigh oxygen concentration

We present an investigation on the influence of the oxygen concentration on radiation-induced changes in the effective doping concentration of silicon detectors. Diodes fabricated from silicon with interstitial oxygen content ranging from below 2 x 10(14) to 9 x 10(17) cm(-3) have been irradiated wi th fast neutrons up to a fluence of 2 x 10(15) cm(-2). Our main interest fo cused on the so-called stable damage component in the change of the effecti ve doping concentration being of prime importance for the application of si licon detectors in high-energy physics experiments. We demonstrate, that wi th a high oxygen enrichment the donor removal is appreciably reduced, reach ing a value of only 10% of the initial doping concentration for [O-i] = 9 x 10(17) cm(-3), while for normal detector grade material with [O-i] below 5 x 10(16) cm(-3) that value is 60-90%. Furthermore, we show that the fluenc e proportional introduction of stable acceptors is independent of the oxyge n concentration with an averaged introduction rate of (1.49 +/- 0.03) x 10( -2) cm(-1). Only one material was found exhibiting a significantly smaller value of about 0.6 x 10(-2) cm(-1) and thus indicating the possibility to s uppress the radiation-induced acceptor creation by material modification. F inally, we show that the experimental findings disagree in several importan t aspects with predictions made by microscopic defect kinetics models, leav ing the physical background of some of the measured data as an open questio n. (C) 2000 Elsevier Science B.V. All rights reserved.