Modeling and optimization of GaN-based betavoltaic batteries: Comparison of p–n and p–i–n junctions

Nuclear battery is a promising long-life power source. Selecting semiconductors with high limit efficiency and appropriate device structures effectively improves their output performance. In this work, a GaN-based (hexagonal) betavoltaic battery with Ni63 source was simulated by Monte Carlo codes and COMSOL Multiphysics, and the energy converters, including p–n junction and p–i–n junction, were compared and optimized. We analyzed the effects of thickness and doping concentration of each region on the battery performances. The p-region and n-region thickness and doping concentration of the p–n junction-based battery are 0.5, 9.5 µm, 1017 cm−3, and Nd = 1016 cm−3, which can achieve 3.77% conversion efficiency, and the short-circuit current density, open-circuit voltage, and maximum output power density are 0.074 µA/cm2, 2.01 V, and 0.125 µW/cm2, respectively. For the p–i–n junction-based battery, when the thickness and the doping concentration of p-region, i-region, and n-region are 0.5, 3, 6.5 µm, 1017, 1014, and 1016 cm−3, respectively, the conversion efficiency, short-circuit current density, open-circuit voltage, and maximum output power density are 5.03%, 0.099 µA/cm2, 2.0 V, and 0.167 µW/cm2, respectively. By comparing the output parameters of the two types of batteries, the results indicate that the p–i–n junction has a wider depletion region and better output performance compared with the p–n junction.