Enhancing charge collection efficiency in radiation-damaged unmetallized 4H-SiC detectors via sub-bandgap LED illumination

A new generation of 4H-SiC radiation detectors has demonstrated stable spectroscopic performance at temperatures up to 450°C, making this material a strong candidate for suprathermal alpha particle diagnostics in fusion environments such as ITER and DEMO. However, ion irradiation introduces defect-related trapping centers, including deep levels and defect clusters, which degrade charge transport and reduce charge collection efficiency, ultimately limiting detector performance under extreme conditions. This work investigates recovery mechanisms in an unmetallized 4H-SiC p-n junction detector irradiated with 3.5 MeV He ++ ions at fluences ranging from 1 × 10 11 to 1 × 10 13 ions/cm 2 and irradiation temperatures between room temperature and 400°C, allowing assessment of damage evolution under different thermal conditions. The detector response was characterized by using ion beam induced charge at room temperature under controlled blue LED illumination at different intensities, enabling systematic evaluation of light-induced effects on charge transport. Results show that optical excitation induces a light-assisted increase in CCE, partially restoring spectroscopic response in heavily damaged regions, with the strongest effect observed at higher trap densities and increasing monotonically with illumination intensity. Comparison with a charge collection model provides additional insight into carrier dynamics in the presence of deep trapping centers, consistent with defects characterized by large capture cross sections and long carrier detrapping times. Overall, light-assisted trapping mitigation emerges as an effective mechanism to enhance detector stability and operational lifetime in harsh fusion-relevant environments. In parallel, dynamic annealing contributes to damage mitigation by reducing defect formation during irradiation rather than repairing pre-existing defects.