Optimal Selection and Experimental Verification of Wide-Bandgap Semiconductor for Betavoltaic Battery

Wide-bandgap semiconductor betavoltaic batteries have a promising prospect in Micro-Electro-Mechanical Systems for high power density and long working life, but their material selection is still controversial. Specifically, the silicon carbide (SiC) betavoltaic battery was reported to have higher efficiency, although its bandgap is lower than that of gallium nitride (GaN) or diamond, which is inconsistent with general assumptions. In this work, the effects of different semiconductor characteristics on the battery energy conversion process are systematically analyzed to explain this phenomenon, including beta particle energy deposition, electron-hole pair (EHP) creation energy and EHPs collection efficiency. Device efficiencies of the betavoltaic battery using SiC, GaN, diamond, gallium oxide (Ga₂O₃), aluminum nitride (AlN) and boron nitride (BN) are compared to determine the optimum semiconductor. Results show that SiC for the betavoltaic battery has higher efficiency than GaN, Ga₂O₃ and AlN because of higher EHPs collection efficiency, less energy loss and fewer material defects, which is the optimal selection currently. SiC betavoltaic batteries were prepared, with the device efficiency having reached 14.88% under an electron beam, and the device efficiency recorded as 7.31% under an isotope source, which are consistent with the predicted results. This work provides a theoretical and experimental foundation for the material selection of betavoltaic batteries.