Modeling of nanoheterojunction betavoltaic cell on GaP with Si and 3C-SiC/Si

In this paper, the electrophysical properties and efficiency of energy converters — betavoltaic elements, which contain a GaN and GaP heterojunction on Si and 3C-SiC/Si substrates, are modeled. For conversion into electrical energy, external ${}^{63}$Ni or internal ${}^{14}$C radioactive sources with a test specific activity of 100 mCi$\cdot$cm$^{-2}$ are investigated in the simulation. The system of parameters and characteristics is optimized: diffusion lengths, short-circuit current, open circuit voltage, filling factor, reverse saturation current and efficiency. It was shown in simulation results, that in the device structure with junction depth of 0.1 microns, the good operation of a betavoltaic element is determined, the short-circuit current density is up to 200 nA$\cdot$cm$^{-2}$, the open circuit voltage is up to 3.7 V, the power density is up to 700 nW$\cdot$cm$^{-2}$, efficiency up to 25 %. The conversion efficiency reaches its maximum value when using a radioisotope source with an activity density from 25 to 100 mCi$\cdot$cm$^{-2}$. The conversion efficiency with the location of the injector source inside is estimated to be about 30 times higher than with the external location.