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Spectroscopic Response Versus Interelectrodic Charge Formation Position in CdTe Detectors

Published online by Cambridge University Press:  10 February 2011

N. Auricchio ,
E. Caroli ,
G. De Cesare ,
W. Dusi ,
D. Grassi ,
M. Hage-Ali ,
E. Perillo ,
P. Siffert  and
G. Spadaccini
N. Auricchio
Affiliation:
Istituto TESRE/CNR, via Gobetti 101, 40129 Bologna, Italy, caroli@tesre.bo.cnr.it
E. Caroli
Affiliation:
Istituto TESRE/CNR, via Gobetti 101, 40129 Bologna, Italy, caroli@tesre.bo.cnr.it
G. De Cesare
Affiliation:
Istituto TESRE/CNR, via Gobetti 101, 40129 Bologna, Italy, caroli@tesre.bo.cnr.it
W. Dusi
Affiliation:
Istituto TESRE/CNR and Sezione INFN, via Gobetti 101, 1-40129 Bologna, Italy
D. Grassi
Affiliation:
Dipartimento di Scienze Fisiche and Sezione INFN, pad. 20, Mostra d'Oltremare, 1 80125 Napoli, Italy
M. Hage-Ali
Affiliation:
Lab. PHASE/CNRS, 23 rue de Loess, F-67037 Strasbourg Cedex 2, France
E. Perillo
Affiliation:
Dipartimento di Scienze Fisiche and Sezione INFN, pad. 20, Mostra d'Oltremare, 1 80125 Napoli, Italy
P. Siffert
Affiliation:
Lab. PHASE/CNRS, 23 rue de Loess, F-67037 Strasbourg Cedex 2, France
G. Spadaccini
Affiliation:
Dipartimento di Scienze Fisiche and Sezione INFN, pad. 20, Mostra d'Oltremare, 1 80125 Napoli, Italy
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Abstract

The electron-hole pair production energy (∼ 4.43 eV) in cadmium telluride semiconductor based detector would allow, in principle, to achieve spectroscopic performance close to germanium. In fact the material impurities, crystal lattice defects and low charge mobility, mainly for holes, can severely degrade the spectroscopic properties through charge trapping/detrapping and recombination phenomena, limiting the usable distance between the electrodes. The charge collection efficiency depends, following the Hecht relation, on the distance between the charge production location and the collecting cathode; we have studied the dependence of some CdTe spectroscopic parameters (energy resolution, photo-peak gain and efficiency) from this distance. A set of experimental tests were performed using a well collimated photon beam. The beam spot, obtained from a 57Co radioactive source through a thick (20 mm) tungsten collimator having a 0.2×2 mm window, was positioned between the two electrodes of a CdTe crystal of size 3×5×2 mm3, with the electrodes deposited on the 3×5 mm2 sides.

The detector was irradiated on the face having the area of 2×3 mm2, in the arrangement with the collecting field orthogonal to the incoming radiation (PTF configuration), and the largest side of the spot parallel to the electrode plane. Using a micro-positioning system a fine scanning of the interelectrodic region was performed.

In order to evaluate the detector behavior in a wider energy range, further tests using energies between 14 keV to 662 keV have been performed.

The results of these measurements are presented and discussed in order to emphasize a method to improve CdTe detector spectroscopic capabilities and to understand the detection behavior

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 487: Symposium I – Semiconductors for Room-Temperature Radiation II , 1997 , 309
Copyright
Copyright © Materials Research Society 1998

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References

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