Radiation‐Induced Degradation and Charge‐Collection Stability in 4H‐SiC p–i–n Betavoltaic Cells

4H‐silicon carbide (SiC)–based betavoltaic (BV) cells have gained attention as self‐powered energy sources for long‐term stable operation in space and extreme environments. In this study, a 4H‐SiC p–i–n BV cell was fabricated, and the degradation mechanisms of its electrical characteristics under proton irradiation were investigated. To emulate the β‐particle spectrum of nickel‐63 (Ni‐63), current density–voltage ( J – V ), and P – V characteristics were measured under electron‐beam (e‐beam) energies of 5–25 keV and various beam currents, while penetration depth and EHP generation were analyzed using CASINO simulations. The defect distribution under 14.8 MeV proton irradiation was evaluated using SRIM, and trap effects on charge transport and output were simulated with Silvaco ATLAS TCAD. Experimental results showed that J sc , V oc , and P max.out all decreased after irradiation because vacancy‐type defects in the intrinsic layer (i‐layer) acted as recombination centers. Simulations showed the same trend, confirming that defects primarily cause performance degradation. Nevertheless, the extended depletion region of the p–i–n structure preserved charge‐collection capability after irradiation, ensuring electrical stability. These results demonstrate the potential of 4H‐SiC as a promising self‐powered energy material with long‐term radiation tolerance.