A betavoltaic device is reported that directly converts beta energy from a 63Ni radioisotope into electrical energy by impact ionization in a GaP nanowire array. The GaP nanowires are grown in a periodic array by molecular beam epitaxy on silicon using the self-assisted vapor-liquid-solid method. By growing GaP nanowires with large packing fraction and length on the order of the maximum beta range, the nanowires can efficiently capture the betas with high energy conversion efficiency while using inexpensive Si substrates. Monte Carlo simulations predict a betavoltaic efficiency in agreement with experimental results. The nanowire betavoltaic device can be used as a power source for nano-/micro-systems such as mobile electronic devices, implantable medical devices, and wireless sensor networks.
- Gallium phosphide