Characterization of Czochralski silicon detectors

Abstract

This thesis describes the characterization of irradiated and non-irradiated segmented detectors made of high-resistivity (>1 kΩcm) magnetic Czochralski (MCZ) silicon. It is shown that the radiation hardness (RH) of the protons of these detectors is higher than that of devices made of traditional materials such as Float Zone (FZ) silicon or Diffusion Oxygenated Float Zone (DOFZ) silicon due to the presence of intrinsic oxygen (> 5 × 1017 cm−3). The MCZ devices therefore present an interesting alternative for future high-energy physics experiments. In the large hadron collider (LHC), the RH of the detectors is a critical issue due to the high luminosity (1034 cm−2s−1) corresponding to the expected total fluencies of fast hadrons above 1015 cm−2. This RH improvement is important since radiation damage in the detector bulk material reduces the detector performance and because some of the devices produced from standard detector-grade silicon, e.g. FZ silicon with negligible oxygen concentration, might not survive the planned operational period of the LHC experiments.

In this work, segmented detectors and test structures were processed, measured, irradiated with different particles (protons of different energies, neutrons and high-energy electrons) and tested with a 60Co gamma source and with high-energy muon and pion beams. The electrical characterizations show that, for proton irradiation, the MCZ silicon is significantly radiation harder than traditionally used detector materials. In gamma irradiation, MCZ silicon detectors behave similarly to the DOFZ silicon detectors. For neutron radiation, there is only a small difference between MCZ silicon and the reference devices made of standard FZ silicon. The beam test results with the full-size detectors show that the properties of the high-resistivity MCZ silicon are suitable for particle detection both before and after heavy proton irradiation.