Modeling and simulation of an InGaP/GaAs heterojunction betavoltaic cell powered by promethium-147

Nuclear microbatteries based on semiconductor heterojunction cells are promising designs to achieve efficient energy conversion of the particles emitted from a radioactive source into electrical energy. Selecting semiconductors with appropriate device structure and radiation source effectively improve their output performance. In this study, we investigated an In0.49Ga0.51P/GaAs betavoltaic heterojunction cell powered by Promethium-147 (Pm147) irradiation, which emits negative beta-particles with an average kinetic energy of 61.93 keV, using a lab-made software. Simulations of cell's current density-voltage J(V) and output electric power P(V) characteristics are carried out using a comprehensive analytical model. The proposed model accounted for ohmic losses, the reflection of incident beta-particles from the front surface, limits of the space charge region, and metallurgical border effects. To optimize the cell's performance, we performed several simulations, varying the doping concentrations and base thicknesses in the device structure and the surface recombination velocities in the front and back regions. Moreover, we assumed different values of the Pm147 apparent activity density. The obtained results are very encouraging showing that Pm147 coupled with InGAP/GaAs heterojunction is very suitable solution for this kind of power generation. Alternative beta radiation sources, namely: H3, Ni63, Co60, Cs137, and Sr90, are also considered for the comparison. The computed electrical power density of the improved cell reaches to 436.66 nW cm-2, while the conversion efficiency is close to 11.91% when irradiated by Pm147. These values could increase to 1441.29 nW cm-2 and 12.43% when Sr90 (Strontium-90) is used as the emitting source.