Recent advancements in the development of radiation hard semiconductor detectors for S-LHC
ABSTRACT The proposed luminosity upgrade of the Large Hadron Collider (S-LHC) at CERN will demand the innermost layers of the vertex detectors to sustain fluences of about 1016 hadrons/cm2. Due to the high multiplicity of tracks, the required spatial resolution and the extremely harsh radiation field new detector concepts and semiconductor materials have to be explored for a possible solution of this challenge. The CERN RD50 collaboration “Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders” has started in 2002 an R&D program for the development of detector technologies that will fulfill the requirements of the S-LHC. Different strategies are followed by RD50 to improve the radiation tolerance. These include the development of defect engineered silicon like Czochralski, epitaxial and oxygen-enriched silicon and of other semiconductor materials like SiC and GaN as well as extensive studies of the microscopic defects responsible for the degradation of irradiated sensors. Further, with 3D, Semi-3D and thin devices new detector concepts have been evaluated. These and other recent advancements of the RD50 collaboration are presented and discussed.
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ABSTRACT: This work focuses on 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 15 MeV electrons, 23 GeV 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 is presented. In particular, it is shown that the changes in the Si device properties (depletion voltage and leakage current) after exposure to high levels of 60Co-γ doses can 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 are the annealing effects which decrease (increase) the originally observed damage effects as seen by the changes of the depletion voltage and these effects are 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 is not affected by the oxygen content or silicon growth procedure suggesting that they are complexes of multi-vacancies located inside extended disordered regions.Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 01/2009;
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ABSTRACT: Diodes fabricated on high resistivity standard, oxygenated and magnetic Czochralski p-type materials were irradiated with reactor neutrons and 24 GeV/c protons up to an equivalent fluence of Φeq=3×1014 cm−2. Radiation effects on effective trapping times, effective dopant concentration and leakage current were measured at 20 °C. Annealing of defects was performed at 20 and 60 °C.Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2009; · 1.14 Impact Factor
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ABSTRACT: A large set of silicon pad detectors produced on MCz and FZ wafer of p- and n-type was irradiated in two steps, first by fast charged hadrons followed by reactor neutrons. In this way the irradiations resemble the real irradiation fields at LHC. After irradiations controlled annealing started in steps during which the evolution of full depletion voltage, leakage current and charge collection efficiency was monitored. The damage introduced by different irradiation particles was found to be additive. The most striking consequence of that is a decrease of the full depletion voltage for n-type MCz detectors after additional neutron irradiation. This confirms that effective donors introduced by charged hadron irradiation are compensated by acceptors from neutron irradiation.Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 01/2009;