The Modeling of Radioisotope Micro Batteries for Microsystems

Conventional direct conversion devices of radioisotope micro battery (RMB) suffer from small surface area and unreliability. In order to solve these problems, a method, which is verified with simulation results, is introduced for modeling the direct conversion devices. The fundamental structure of RMB is presented, and the equations of current are founded. The novel direct conversion device of vertical wall array is demonstrated. As a result, 171% increase of the surface area is acquired and the reliability is enhanced owing to the electro plating section. Simulation is performed to investigate the performance of RMB with the source density of 1mCi/mm². Optimization of the method has resulted in that the optimum doping concentrations are N_A=10¹⁷/cm³ and N_D=10¹⁷ /cm³. Simulation results predicts that the method based the novel direct conversion device can get a V_OC (open circuit voltage) of 180mV, a J_SC (short circuit current density) of 3nA/mm² and P^m (output power density) of 0.4nW/mm² within a volume of 0.1mm³