Planar Homojunction Gallium Nitride (GaN) P-i-N Device Evaluated for Betavoltaic Energy Conversion: Measurement and Analysis

Abstract : Isotope power sources provide a continuous flow of energy from decaying isotopes. The operational lifetimes of these power sources are measured in decades, not years. The energy density of isotopes (J/kg) is 106 greater than that of chemical batteries. The energy emitted in the decay of low-energy betas from tritium (3H) and nickel-63 (63Ni) is converted to a trickle charge of electric current. The report describes initial measurements of energy collected in a planar homojunction gallium nitride (GaN) device. The parametric variation of electron beam energy (2.5-16 keV) enables correlation to the beta spectra of both 3H and 63Ni natural decay products. The analysis of the specific isotope-weighted electron beam distribution described predicts the power efficiency of the device structure as a 2-D isotope power source system. This first look at GaN device geometries suggests that optimization of device geometry in subsequent designs will employ a 3-D structure using novel growth techniques along the material crystal axis.