Signal Multiplication in Irradiated SiC Diodes

This study explores signal amplification mechanisms in neutron-irradiated silicon carbide (SiC) p-in-n planar diodes using TPA-TCT under both reverse and forward bias conditions. After irradiation, SiC devices exhibit strong carrier trapping, particularly affecting hole transport. Remarkably, under forward bias, an enhancement of the collected charge is observed near the n⁺ contact, suggesting the onset of hole-driven avalanche multiplication in regions of high electric field. This hypothesis is supported by charge collection profiles and the observed asymmetry in signal dependence on drift direction. Optical injection of carriers using continuous UV light confirms the asymmetry in electron and hole lifetimes post-irradiation, with holes dominating the multiplication process. The combined analysis of transient current signals, charge-bias characteristics, and carrier injection responses provides compelling evidence for gain effects in irradiated SiC detectors. These findings open the possibility of engineering internal gain in wide bandgap detectors through controlled forward biasing and field shaping, offering a path toward enhanced performance in high-radiation environments.