Relatore
Dr.
Jiaguo Zhang
(Paul Scherrer Institut)
Descrizione
Recent progress in the fabrication of fine-pitch CdTe sensors and the development of bonding technology makes this material a good candidate for hybrid pixel detector systems, in particular for imaging experiments at synchrotrons (or free-electron lasers) with X-ray energy up to a few hundred keV. The main drawbacks of CdTe sensors in terms of their electrical performance are the high leakage current for pixel electrodes fabricated by ohmic contact, and the time dependence of charge collection caused by biasing and flux for electrodes fabricated by Schottky contact. The latter is also known as the polarization effect. To properly simulate and understand both effects, and to optimize the sensor layout in the future, the knowledge and implementation of traps into simulation is essential. In this work, the Cd vacancies (Vcd), Vcd-donor complexes, deep traps as well as residual impurities have been considered. The concentration of deep traps is calibrated by comparing the material resistivity of simulation and measurement on a Cl-doped CdTe pad sensor produced by Acrorad. Based on this result, the polarization effect has been simulated and explained. In addition, the charge collected by edge pixels and their non-uniformity compared to central pixels, which is caused by the change in resistivity at the edge of the sensor, has been studied and compared to measurements. Finally, the validation and limit of the trap model and its influence on sensor-layout optimization are discussed.
Autore principale
Dr.
Jiaguo Zhang
(Paul Scherrer Institut)
Coautore
Aldo Mozzanica
(Paul Scherrer Institut)
Anna Bergamaschi
(Paul Scherrer Institut)
Bernd Schmitt
(Paul Scherrer Institut)
Christian Ruder
(Paul Scherrer Institut)
Davide Mezza
(Paul Scherrer Institut)
Davit Mayilyan
(Paul Scherrer Institut)
Dhanya Thattil
(Paul Scherrer Institut)
Dominic Greiffenberg
(Paul Scherrer Institut)
Erik Fröjdh
(Paul Scherrer Institut)
Gemma Tinti
(Paul Scherrer Institut)
Lukas Schaedler
(Paul Scherrer Institut)
Marco Ramilli
(Paul Scherrer Institut)
Martin Brueckner
(Paul Scherrer Institut)
Roberto Dinapoli
(Paul Scherrer Institut)
Sebastian Cartier
(Paul Scherrer Institut)
Sophie Redford
(Paul Scherrer Institut)
Xintian Shi
(Paul Scherrer Institut)