Planar Homojunction Gallium Nitride (GaN) P-i-N Device Evaluated for Betavoltaic Energy Conversion: Measurement and Analysis
US Army Research Laboratory Adelphi United States
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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 Jkg 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.