ELECTROPLATING NICKEL ONTO GALLIUM ARSENIDE AND GALLIUM PHOSPHIDE NANOWIRES FOR BETAVOLTAIC APPLICATIONS

Abstract

Betavoltaic (BV) devices represent a promising alternative energy technology, offering long-lasting, maintenance-free power for applications in remote, harsh, or inaccessible environments. Their performance is often limited by self-absorption of beta particles and inefficient carrier collection in conventional planar geometries. To address these challenges, this work investigates the conformal electroplating of nickel (Ni), and ultimately radioisotope nickel-63 in the future, onto gallium arsenide (GaAs) and gallium phosphide (GaP) NWs for use in BV devices. A systematic evolution of electroplating cell designs - from a simple beaker configuration to a custom Teflon cell - was carried out to optimize uniformity, reproducibility, and current efficiency. Direct current (DC) and pulsed electroplating methods were evaluated across NW arrays of varying pitch (360 nm, 600 nm, and 1000 nm). Results demonstrate that pulsed electroplating significantly mitigates mass diffusion limitations compared to DC plating, improving conformality along NW sidewalls. Optimal plating conditions were found to depend strongly on the interplay between on-time, off-time, and lateral diffusion times within NW arrays. These findings provide a framework for achieving controlled Ni coatings on III–V NWs, representing a key step toward high-efficiency, nanoscale BV devices.