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Real-time Imaging of the Electric field Distribution in CdZnTe at low temperature

Published online by Cambridge University Press:  31 January 2011

Paul Sellin
Affiliation:
p.sellin@surrey.ac.uk, University of Surrey, Department of Physics, Guildford, United Kingdom
Georgios Prekas
Affiliation:
g.prekas@surrey.ac.uk, University of Surrey, Department of Physics, Guildford, United Kingdom
Annika Lohstroh
Affiliation:
a.lohstroh@surrey.ac.uk, University of Surrey, Department of Physics, Guildford, United Kingdom
Ersin Ozsan
Affiliation:
m.e.ozsan@surrey.ac.uk, University of Surrey, Department of Physics, Guildford, United Kingdom
Perumal Veeramani
Affiliation:
p.veeramani@surrey.ac.uk, University of Surrey, Department of Physics, Guildford, United Kingdom
Matt Veale
Affiliation:
matthew.veale@stfc.ac.uk, STFC Rutherford Appleton Laboratory, Instrumentation Department, Harwell, United Kingdom
Paul Seller
Affiliation:
paul.seller@stfc.ac.uk, STFC Rutherford Appleton Laboratory, Instrumentation Department, Harwell, United Kingdom
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Abstract

Real time imaging of the electric field distribution in CZT at low temperature has been carried out using the Pockels electro-optical effect. CZT detectors have been observed to show degraded spectroscopic resolution at low temperature due to so-called ‘polarization’ phenomena. By mounting a CZT device in a custom optical cryostat, we have used Pockels imaging to observe the distortion of the electric field distribution in the temperature range 240K - 300K. At 240K the electric field has a severely non-uniform depth distribution, with a high field region occupying ∼10% of the depth of the device under the cathode electrode and a low field in the remainder of the device. Using an alpha particle source positioned inside the vacuum chamber we have performed simultaneous alpha particle transient current (TCT) measurements. At low temperatures the alpha particle current pulses become significantly shorter, consistent with the reduced electron drift time due to a non-uniform electric field. These data provide useful insights into the mechanisms which limit the spectroscopic performance of CZT devices at reduced temperature.

Type
Research Article
Copyright
Copyright © Materials Research Society 2009

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