D–T Neutron and 60Co-Gamma Irradiation Effects on HPSI 4H-SiC Photoconductors

The 14.1-MeV neutron irradiation- and
⁶⁰
Co- gamma irradiation-produced traps in high-purity semi-insulating (TIPS!) 4TI-SiC photoconductors (PCs) are reported, and the irradiation-induced changes in substrate resistivity, dark current, and UV response of the 4TI-SiC PCs are analyzed. From the zerobias thermally stimulated current measurements, six new traps at the energy levels Ev + 0.58 eV, E
_v
+ 0.68 eV, E
_v
+ (0.7-0.9) eV, E
_c
- 0.64 eV, Ec - 0.91 eV, and E
_c
- 1.0
⁴
eV are identified in the 14.1-MeV neutron-irradiated PCs at the fluence of 10
¹¹
n/cm
²
, along the defects already detected before neutron irradiation. The thermal activation energy range (1-1.3 eV) for HPSI 4TI-SiC is unaffected, and no considerable changes in the UV response of the PCs are noticed after the 14.1-MeV neutron irradiation. On the other hand, in addition to the traps determined prior to the irradiation, one new deep hole trap at E
_v
+1.31 eV and significant changes in the activation energies (1.1-1.35 eV) are observed in the gamma-irradiated PCs at the dose of 100 Mrad, which suggest that the HPSI 4TI-SiC substrate resistivity is increased due to the gamma irradiation-produced traps. Moreover, the signal-to-dark current ratio of the PCs is reduced after the gamma irradiation, as inferred from the UV response of the PCs.