Theoretical study on the selective emitter radioisotope micro battery

Radioisotope micro battery has the capability of meet the requirements of micropower. This paper investigated the two distinct parts and the structure characteristics of the selective emitter radioisotope micro battery. Compared with the conventional Back Surface Filed radioisotope micro battery, the selective emitter radioisotope micro battery has two distinct parts: (1) a deeply diffused region with high surface doping concentration under the metal contacts and the adjacent region; (2) a surface passivated, shallow diffused region with a relatively low surface doping concentration in active region. Thus formed a lateral n⁺-n junction between the heavily diffused region and the shallow diffused region, a n⁺-p junction under the metal contacts, and a p-n junction at the other regions as the same as the conventional Back Surface Field radioisotope micro battery. Therefore, compared with the conventional Back Surface Field radioisotope micro battery, the selective emitter radioisotope micro battery has a lot of advantages: (1) improve the collection efficiency of the electron hole pairs; (2) improve the output voltage of the radioisotope micro battery; (3) reduce the series resistance of the radioisotope micro battery; (4) reduce the surface recombination rate of the electron hole pairs; (5) reduce the effect of the diffusion dead layer, thus improve the overall performance of the diffusion layer. In conclusion, the selective emitter structure is proved to be one of the effective ways to improve the conversion efficiency of radioisotope micro battery in the course of deeply analyzing on its advantages.