Speaker
Description
The 4H-polytype of SiC still remains a promising semiconductor material for detector preparation. Its wide band-gap (3.23 eV @ room temperature) predestines it for operation not only at room temperature but also at rather high temperatures up to several hundred degrees Celsius. High breakdown voltage (4 MV/cm) leads to high drift velocity of radiation-generated charge carriers and so to fast detector response. The 4H-SiC stands out in a high atomic displacement energy (20-35 eV) among semiconductor materials, which makes it very promising in terms of resistance against radiation damage. However, the defects in semiconductor structure cause noise signal and their concentration should not exceed 1e14 cm-3 to ensure reasonable signal to noise ratio during radiation detection. In the case of SiC, this condition is at the edge of recent production technology limits. We have prepared single pad Schottky type detectors based on 4H-SiC material of sufficient quality prepared as 80 µm thick epitaxial layer on base material substrate. The Schottky electrode of 3 mm diameter was created as an Au/Ni double layer evaporated on the top side (epitaxial layer) of the wafer and the full area ohmic contact of Ti/Pt/Au was deposited on its back side. Measured current-voltage characteristic of prepared structures have shown that the reverse current flowing through the structures is in the range of pA which enables to achieve very good pulse-height spectrometry. The exceptional thermal and radiation resistance of SiC as a semiconductor material implies its application as a detector in today’s nuclear reactors, fusion or fission ones, or in other radiation and thermally harsh technologies. The SiC detectors have shown suitability as detectors of fast neutrons. The atoms of the material react as targets for neutron conversion and the products of neutron absorption and scattering are created directly in the detector volume. We have tested the fabricated 4H-SiC detectors with two neutron sources, the Van de Graaff accelerator of CTU in Prague, producing neutrons through T(p,n), D(d,n) and T(d,n) nuclear reactions and the DANAIDES T(d,n) generator at CEA in Cadarache, in the frame of the 'Timepix SiC detector' international project under the DANUBE2022 region strategy programme. The given reactions at multiple projectile energies were chosen to obtain the numerous responses of the detectors to fast neutrons in the entire range of energies from 0.3 to 17 MeV, to evaluate detector suitability for neutron classification in neutron fields. The response of SiC detector was analysed and compared with the responses of commercially available reference Si diode and with a single crystal diamond detector fabricated at SAS in Bratislava. All these three detectors were placed in the same relative position with respect to neutron source and have been exposed to the neutrons of the same energies during measurement. The pulse-height spectra measured by silicon detector and diamond detector separately, have confirmed the interpretation of the structure of the pulse-height spectra measured by the SiC detector, merging the interaction of neutrons on both types of SiC nuclei together: on silicon in reference silicon detector and on carbon in diamond detector. Besides, the two target nuclei as a part of SiC detector volume increase the amount of the reactions to be used for fast neutron spectrometry enabling to achieve more precise results.
The authors would like to acknowledge the support by the Slovak Research and Development Agency under the Contract no. DS-FR-22-0012.
