The design optimization for GaN-based betavoltaic microbattery

In this paper, we demonstrate a p-n junction betavoltaic microbattery which is based on the wide-band gap material of GaN. Ni-63 was used as the pure beta radiant source. By the Monte Carlo (MC) simulation, the trajectories of single-energy electron beam incident on GaN target, the averaging penetration depth and the energy deposition along the penetration path were obtained. According to them, the optimal p-n junction depth was designed. To compare with the design, we have fabricated GaN betavoltaic cells using the metal-organic, chemical-vapor deposition (MOCVD) and the GaN micromachining technology. Under an activity of 11mCi Ni-63 source irradiation, the open circuit voltage of 25 mV and short circuit current of 2 nA were measured in a single 1*1 cm cell which are far apart from designed values 475 mV and 56 nA. Methods to further increase the performance of the GaN betavoltaic microbattery were discussed.