Ni-63 radioisotope betavoltaic cells based on vertical electrodes and pn junctions

3D Silicon pn junction betavoltaic cells are designed and fabricated with vertical electrode structure in this work. The betavoltaic cells consist of multiple vertical pn junctions generated by the vertical p-electrodes. The beta-particles from beta-emitting radioisotope Ni-63 are directly incident to the space charge region of vertically generated pn junctions without passing the neutral n or p region. The energy conversion from nuclear energy to electric energy occurs at the vertically generated space charge region. The electrical characteristics of betavoltaic cells having three different unit pn electrode spacing, i.e. 50, 110, and 190µm are demonstrated using electron beam irradiation in a scanning electron microscope (SEM). The Voc and Jsc as a function of pn spacing under 17keV and 30keV of acceleration voltage onto 1.2 × 1.2 mm2 of unit cell absorption area are presented in this paper.