A study of the carrier transport mechanism, the charge collection efficiency and the energy resolution has been carried out on semi-insulating GaAs X-ray detectors realised on substrates with concentrations of acceptor dopants N-a, varying from 10(14) to 10(17) cm(-3). The electron collection efficiency (ECE) and the reverse current were found to decrease with increasing N-a, while the resistivity of the material was found to increase. At room temperature, the best collection efficiency (95%) and the best energy resolution (13.7 keV FWHM) for 59.5 keV X-rays of the Am-241 source, have been achieved with the less doped detectors (N-1 - 10(14) cm(-3)). The concentrations of ionised EL2(+), determined by optical measurements in IR regions, was shown to increase with N-a and to be quasi-inversely proportional to the ECE values. This behaviour strongly supports the hypothesis that the EL2 defects play a main role in the compensation of the material and in the limitation of the detection properties. (C) 2000 Published by Elsevier Science B.V. All rights reserved.
Influence of substrate on the performance of semi-insulating GaAs detectors / R., Baldini; P., Vanni; Nava, Filippo; Canali, Claudio; C., Lanzieri. - In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH. SECTION A, ACCELERATORS, SPECTROMETERS, DETECTORS AND ASSOCIATED EQUIPMENT. - ISSN 0168-9002. - 449:1-2(2000), pp. 268-276. [10.1016/S0168-9002(99)01443-6]
Influence of substrate on the performance of semi-insulating GaAs detectors
NAVA, Filippo;CANALI, Claudio;
2000
Abstract
A study of the carrier transport mechanism, the charge collection efficiency and the energy resolution has been carried out on semi-insulating GaAs X-ray detectors realised on substrates with concentrations of acceptor dopants N-a, varying from 10(14) to 10(17) cm(-3). The electron collection efficiency (ECE) and the reverse current were found to decrease with increasing N-a, while the resistivity of the material was found to increase. At room temperature, the best collection efficiency (95%) and the best energy resolution (13.7 keV FWHM) for 59.5 keV X-rays of the Am-241 source, have been achieved with the less doped detectors (N-1 - 10(14) cm(-3)). The concentrations of ionised EL2(+), determined by optical measurements in IR regions, was shown to increase with N-a and to be quasi-inversely proportional to the ECE values. This behaviour strongly supports the hypothesis that the EL2 defects play a main role in the compensation of the material and in the limitation of the detection properties. (C) 2000 Published by Elsevier Science B.V. All rights reserved.
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