Demonstration of a GaN betavoltaic microbattery

A GaN-based betavoltaic microbattery was demonstrated. The wide-band gap semiconductor of GaN and pure beta radioisotope source of ⁶³Ni were used as the converter and the energy source. The GaN-based p-i-n junction wafers were epitaxially grown by metal-organic, chemical-vapor deposition (MOCVD) on the 2-inch c-plane sapphire substrates. Under the irradiation of an activity of 2mCi (about 0.13mCi/mm²) ⁶³Ni source, an open-circuit voltage of 474mV and a short-circuit current density of 17nA/cm² were measured in a fabricated single 1×1 mm² cell, and the calculated conversion efficiency of 1.8% lower bound can be obtained. The results suggest that the wide-band gap semiconductor of GaN is a high potential candidate of betavoltaics for big open-circuit voltage and high efficiency.