Electron beam irradiation of gallium nitride-on-silicon betavoltaics fabricated with a triple mesa etch

A process for growing gallium nitride (GaN) vertical p-i-n homojunctions on (111) silicon substrates using metalorganic chemical vapor deposition was developed, and a triple mesa etch technique was used to fabricate efficient betavoltaic energy converters. Monte Carlo simulation platform CASINO was used to model beta radiation penetration into GaN to aid device design. The resulting devices were tested under irradiation from a scanning electron microscope electron beam (e-beam) tuned to imitate the energies of the Ni-63 beta emission spectrum. Based on current-voltage measurements taken under e-beam illumination, a maximum open-circuit voltage of similar to 412 mV and a maximum short-circuit current density of similar to 407 nA/cm(2) were measured. A high fill factor of similar to 0.77 and power conversion efficiency of similar to 6.6% were obtained. Additionally, the proposed triple mesa etch technique used to create these betavoltaics has the potential for further use in fabricating many types of electronic devices using a wide variety of material platforms.