Electrically active defects in neutron-irradiated HPSI 4H-SiC X-ray detectors investigated by ZB-TSC technique

Electrically active defects in high-purity semi-insulating (HPSI) 4H-silicon carbide (4H-SiC) X-ray detectors have been characterized before and after neutron irradiation by zero-bias thermally stimulated current (ZB-TSC) and high-temperature resistivity measurements. The ZB-TSC measurements prior to irradiation reveal nine hole traps in the energy range of 0.22-1.16 eV and two electron traps at E_c-0.35 eV and E_c-0.44 eV. For the same case, high-temperature resistivity measurements yield thermal activation energy in the range of 1-1.3 eV. It is considered that the hole traps at E_v+ 0.83 eV and E_v+ 1.16 eV along with defects located near the activation energies are possibly responsible for the substrate compensation. A poor resolution of 11.8-keV full-width at half-maximum (at 40 keV of ¹⁵²Eu) with un-irradiated HPSI 4H-SiC detectors is attributed to the charge trapping and polarization effects. After neutron irradiation at the fluence of 10^{11} n/cm², seven new traps ( E_v+ 0.68 eV, E_v + 1.08 eV, E_v + 1.22 eV, E_c-0.72 eV, E_c- 0.9 eV, E_c- 1.04 eV, and E_c- 1.1 eV) are identified with no significant changes in the activation energies. This indicates that the substrate resistivity is unaffected by the neutron-irradiation-induced defects. No considerable changes in the X-ray spectral response are noted at 10¹¹} n/cm².