Design considerations on 4H-SiC-based p–n junction betavoltaic cells

In this work, we have theoretically evaluated the performance of a betavoltaic 8 µm-thick p-n structure in silicon carbide 4H (4H-SiC) irradiated by different nickel-63 (Ni63) beta particle sources. The apparent average energy of the emitted beta particles is in the range 18.44–29.94 keV considering the self-absorption effect. By taking into account the reflection on the frontal surface as well as the limits of the depletion region, and by using an equivalent circuit that supports the ohmic losses, the simulations reveal that with the use of a Ni63 radioactive source, with a radioactivity density of 18.76 mCi/cm2, the conversion efficiency (ɳ) exceeds 20%. For the optimized cell, the other important electrical parameters, namely the short-circuit current density (Jsc), the open-circuit voltage (Voc), fill factor (FF) and the maximum electrical power density (Pmax), are 0.299 µA/cm2, 2.4 V, 93.79% and 0.675 µW/cm2, respectively.