| Silicon carbide (SiC) is a wide bandgap semiconductor with good anti-radiation ability. Due to its wide bandgap, the expected open circuit voltage of SiC PiN junction radioisotope battery is high. The battery also has strong anti-interference ability, hardly affected by the outside temperature, pressure and electromagnetic field. The battery has a prospective future.SiC radioisotope battery with the PiN structure is studied in this paper, main research achievements are as follow:The energy deposition of mono-energetic electrons in metals are simulated with MCNP, proving that metal has a strong stopping power, 5 different electrode patterns are designed based on the conclusion; Energy deposition ofβ-ray emitted from Ni-63 is simulated, the result indicates that the energy deposited in SiC decreases exponentially with penetration depth. In order to achieve high charge collection efficiency, the depletion region should be near the surface. Based on the simulation, the thickness of p+ layer and i layer are designed to be 0.3μm and 3.5μm respectively.Basic model of the micro radioisotope battery is built, and the performance of the designed battery is estimated base on the model. Effect of ideality factor, series resistance, shunt resistance, radioactivity on the battery is analysed, the simulated result indicates that: the greater the ideality factor is, the higher the output voltage is; small series resistance has little effect on the performance, but the fill factor (FF) reduces significantly when the resistance is bigger than 5×107Ω; shunt resistance mainly affect fill factor, the larger the resistance, the bigger the fill factor; leakage current mainly affect open circuit voltage, the smaller the leakage current, the larger the open circuit voltage; increasing radioactivity will improve both open circuit voltage and short current, with the short circuit current improved more significantly.Major key processes during the fabrication of radioisotope battery is studied, we decide to form the PiN structure via Chemical Vapor Deposition (CVD), use mesa structure to isolate different devices, use 50/100/100nm Ti/Al/Au as p type ohmic contact metals and 50/400/100nm Ti/Ni/Au as n type ohmic contact metals. The fabrication process is designed, photomask is made and the 4H-SiC PiN junction radioisotope battery is fabricated.The sample is tested, TLM test result shows that good p type ohmic contact is formed with the lowest specific contact resistance of only 2, this value is in the domestic leading level, and close to the lowest specific contact resistance of p type SiC. I-V curve obtained shows the turn on voltage is about 3V, ideality factor 2.4 and leakage current 10-13A/cm2。Under the illumination of 10mCi Ni-63 source that takes up 2.5cm2, the open circuit voltage Voc=0.98V, short circuit current Isc=0.51nA (Jsc =12.75nA/cm2 ), maximum power Pmax=0.32nW (power density is 8.0nW/cm2),and fill factor FF=0.64. Under the illumination of 6mCi Ni-63 source that takes up 2.5cm2, the open circuit voltage is Voc=0.95V, the short circuit current Isc=0.21nA (Jsc =5.25nA/cm2), maximum power Pmax=0.14nW (power density is 3.5nW/cm2),and fill factor FF=0.74. 2.567×10-5ΩcmOther kinds of SiC devices based onβ-voltaic effect are studied. Improvement solution of conventional schottkyβ-voltaic battery is provided. SiC transistor used forβray detector is also designed.
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