4H-SiC p–n junction betavoltaic micro-nuclear batteries based on 14C source with enhanced performance

The long half-life and the high decay energy of beta sources play a critical role in improving the performance of betavoltaic micro-nuclear batteries. In this study, the pure beta source 14C in the form of powder, which can be transformed into an ultra-thin film by using (14C6H5NH)2CO, was selected to design planar 4H-SiC p–n junction betavoltaic batteries. A comprehensive model was developed utilizing the Monte Carlo code and the COMSOL Multiphysics code to predict the output performance. As a result, based on a 100 μm-thick (14C6H5NH)2CO source with a maximum power density of 1.86 μW/cm2 and the current fabrication technology of 4H-SiC p–n junction, we optimized the thicknesses of the p−-type region (4.2 µm) with a doping concentration of Na = 3 × 1016 cm−3 and the n−-type region (5.8 µm) with a doping concentration of Nd = 2 × 1014 cm−3. The corresponding predicted performance values included the short-circuit current density of 0.1 μA/cm2, the open-circuit voltage of 2.15 V, and the maximum power density of 0.2 μW/cm2. Moreover, the energy conversion efficiency of the semiconductor converter can reach 10.6%, while the overall battery efficiency was determined to be 2.9%. Therefore, this research provides a feasible structure for a planar 4H-SiC p–n junction energy converter utilizing the (14C6H5NH)2CO source and presents a powerful model for predicting the performance of planar betavoltaic batteries.