3D GaN-based betavoltaic device design with high energy transfer efficiency.

A combined GaN 3D core-shell and planar pin structure is being developed and demonstrated to achieve the highest potential to increase energy transfer efficiency from the source (η) and power generated per cm (P/cm) in a betavoltaic (BV) device configuration. Physics-based Sentaurus TCAD and Monte Carlo N-Particle extended (MCNPX) software are employed to obtain the maximum η and P/cm by a parametric study of device dimensions coupled with a NiCl source. Idealized structure dimensions are determined to be 2 µm wide, 4 µm tall GaN pin core-shell mesas, with Ni source conformally surrounding the structure with a 2 µm gap for maximum efficiency of energy transfer. For maximizing power deposited (10 µm mesa separation) a 3.75x increase in P/cm at approximately half the activity density compared to a planar device is achieved for 4 µm mesa height, with 5.82x improvement in η.