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Spectroscopic performance studies of 4H-SiC detectors for fusion alpha-particle diagnostics
September 20,2017 



Schottky barrier diode (SBD) detectors are fabricated on n-type 4H-SiC epilayer.

Bulk detectors are fabricated on the HPSI 4H-SiC substrate.

Spectroscopic performances of SBD and bulk detectors are studied using 241Am.

Investigations on polarization in SBD and bulk detectors are performed.

Neutron irradiation effects on the detector properties are analyzed up to 1011 n/cm2.

Device simulations are carried out up to a neutron fluence of 2×1015n/cm2 to predict the survival of the SBD detectors at higher irradiation levels.

The spectroscopic performances of Schottky barrier diodes (SBDs) and bulk detectors fabricated on n-type epitaxial 4H-SiC and high-purity semi-insulating (HPSI) 4H-SiC substrates are studied using 241Am alpha-particles. The spectral responses of the SBD detectors reveal a good energy resolution of 55 keV FWHM (1%) at −60 V, and 90% charge collection efficiency (CCE) at −100 V. The collected signal charge is stable with time in the SBD detectors; hence polarization effects are not noticed, indicating the good crystalline quality of the epitaxial 4H-SiC for detector applications. On the contrary, a poor energy resolution of 675 keV FWHM (12.3%) at −400 V and a maximum CCE of 28% at −500 V are obtained for the bulk detectors. Moreover, the CCE is found to decrease with time after the application of bias voltage implying the polarization phenomenon. Accordingly, the steady-state CCE of the bulk detectors at −500V is decreased to 13% from its initial value. The inferior spectral response of the bulk detectors is possibly due to the charge trapping and polarization effects. Furthermore, the neutron irradiation effects on the α-particle spectral response of the detectors are examined up to a fluence of 1011 n/cm2. To study the reliability of the SBD detectors at higher irradiation levels, the 14.1 MeV neutron irradiation induced changes in the electrical characteristics of the SBD are investigated up to a fluence of 2×1015n/cm2 by device simulations and the probable degradation in the detector response is analyzed. Finally, the possibility of employing 4H-SiC detectors for the fusion alpha-particle diagnostics is discussed.
Keywords:4H-silicon carbide,Alpha-particle detector,Plasma diagnostics,Charge collection,Polarization,Device simulation,
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