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Title: The two sides of silicon detectors
Author: Devine, Steven R. H.
ISNI:       0000 0001 3422 9960
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2001
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Results are presented on in situ irradiation of silicon detector's at cryogenic temperature. The results show that irradiation at cryogenic temperatures does not detrimentally effect a silicon detectors performance when compared to its irradiation at room temperature. Operation of silicon devices at cryogenic temperatures offers the advantage of reducing radiation-induced leakage current to levels of a few pA, while at 130K the Lazarus Effect plays an important role i.e. minimum voltage required for full depletion. Performing voltage scans on a 'standard' silicon pad detector pre- and post-annealing, the charge collection efficiency was found to be 60% at 200V and 95% at 200V respectively. Time dependence measurements are presented, showing that for a dose of 6.5x10e14 p/cm2 (450GeV protons) the time dependence of the charge collection efficiency is negligible. However, for higher doses, 1.2x10e15 p/cm2, the charge collection efficiency drops from an initial measured value of 67% to a stable value of 58% over a period of 15 minutes for reversed biased diodes. An analysis of the "double junction" effect is also presented. A comparison between the Transient Current Technique and an X-ray technique is presented. The double junction has been observed in p+/n/n+ silicon detectors after irradiation beyond "type inversion", corresponding to a fluence equivalent to ~3xl013cm-2 1MeV neutrons, producing p+/p/n+ and essentially two p-n junctions within one device. With increasing bias voltage, as the electric field is extending into the detector bulk from opposite sides of the silicon detector, there are two distinct depletion regions that collect charge signal independently. Summing the signal charge from the two regions, one is able to reconstruct the initial energy of the incident particle. From Transient Current measurements it is apparent that E-field manipulation is possible by excess carrier injection, enabling a high enough E-field to extend across the width of the detector, allowing for efficient charge collection.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available