Modeling and Optimization of ¹⁴⁷Pm Radioisotope-Powered GaN-Based PIN Junction Betavoltaic Cell

Micro nuclear batteries are primarily designed to provide long-term, stable power supplies for microdevices operating in extreme environments. Currently, increasing the power output of nuclear batteries is essential for their broader application. This study investigates the output characteristics of the gallium nitride (GaN)-based PIN junction betavoltaic battery powered by ¹⁴⁷Pm radioactive sources. Based on Monte Carlo (Geant4) and technology computer-aided design (TCAD), we calculate the J-V characteristics of the betavoltaic battery under various radioactive source and transducer structural parameters. Notably, we analyze the impact of traps in the GaN on the battery output.

The results indicate that when the ¹⁴⁷Pm source thickness approaches 10 μm, the surface power output density nearly reaches its maximum. Under irradiation from a source of this thickness, and without considering transducer traps, the device achieves a maximum output power density P_max of 35.68 ± 0.3 μW/cm² and a device energy conversion efficiency η_d of 6.69% ± 0.06%, significantly surpassing the output of ⁶³Ni-based cells. Considering transducer traps, P_max decreases to 22.81 μW/cm². The acceptor trap H1 (energy level: E_v + 0.86 to 0.88) formed during the growth process is found to be the primary factor reducing battery performance.