Electrically Active Defects in Neutron Irradiated HPSI 4H-SiC X-ray Detectors Investigated by ZB-TSC Technique

Abstract

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 $\text{E}_{c} -0.35$ eV and $\text{E}_{c} -0.44$ 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 $\text{E}_{v}+ 0.83$ eV and $\text{E}_{v }+ 1.16$ 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 ( $\text{E}_{v}+ 0.68$ eV, $\text{E}_{v} + 1.08$ eV, $\text{E}_{v} + 1.22$ eV, $\text{E}_{c} -0.72$ eV, $\text{E}_{c} - 0.9$ eV, $\text{E}_{c} - 1.04$ eV, and $\text{E}_{c} - 1.1$ 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 $10^{11}$ n/cm2.