Optimization and experimental demonstration of mesh-patterned 4H-SiC betavoltaic cells for enhanced power density

Betavoltaic (BV) cells based on wide-bandgap semiconductors are promising power sources for long-term operation in harsh environments, yet their energy-conversion efficiency remains below the theoretical limit because only a fraction of β-generated carriers are collected in the depletion region. Here, we propose a mesh-patterned 4H silicon carbide (4H-SiC) BV cell in which the top p-SiC layer is patterned into a two-dimensional mesh, and evaluate its performance using three-dimensional technology computer-aided design (3D TCAD) simulations and measurements of fabricated devices. Generation profiles for 5, 17, and 25 keV electron-beam irradiation, representing the Ni-63 β spectrum, are obtained from CASINO simulations and implemented in Silvaco ATLAS. By sweeping the mesh opening width and the i- and p-layer thicknesses, we identify an optimized geometry yielding a maximum output power density P_{out_max} ≈ 2.60 µW/cm² at 17 keV. Relative to a conventional planar p-i-n cell, the mesh-type cell shows simulated P_{out_max} enhancements of 32.5%, 2.49%, and 0.35% at 5, 17, and 25 keV, and measured enhancements of 65.1%, 4.57%, and 4.32%, respectively. These results demonstrate that a p-layer mesh pattern is an effective structural route to enhance the efficiency of Ni-63-based 4H-SiC betavoltaic cells.