High efficiency high power 4H-SiC betavoltaics using tritium radioisotopes (Conference Presentation)

Applications for stand-alone systems with small form factor, long lifetime and high energy density have arisen. Nuclear batteries have the potential to achieve specific powers of 1-50mW/g and devices that utilize the beta emitter titanium tritide (TiT2) have the most potential. We present our progress in making textured TiT2 based devices and their performance as compared to planar devices. In planar devices a 200nm 4H-SiC P+N junction is used for charge collection. Dark current measured less than 6.1 pA/cm2. Samples measured with tritium foil produced an open circuit voltage of 2.09V, short circuit current of 75.47nA/cm2, fill factor of 0.86 and power efficiency of 18.6%. This device is near the practical limit efficiency. In order to increase the power output the effective area of the beta source is increased by patterning the topmost absorption layer into channels 10 micron in height. Textured devices achieved open circuit voltage of 1.91V and short circuit current of 11.3nA.