AlGaAs (55)Fe X-ray radioisotope microbattery

This paper describes the performance of a fabricated prototype Al(0.2)Ga(0.8)As (55)Fe radioisotope microbattery photovoltaic cells over the temperature range −20 °C to 50 °C. Two 400 μm diameter p(+)-i-n(+) (3 μm i-layer) Al(0.2)Ga(0.8)As mesa photodiodes were used as conversion devices in a novel X-ray microbattery prototype. The changes of the key microbattery parameters were analysed in response to temperature: the open circuit voltage, the maximum output power and the internal conversion efficiency decreased when the temperature was increased. At −20 °C, an open circuit voltage and a maximum output power of 0.2 V and 0.04 pW, respectively, were measured per photodiode. The best internal conversion efficiency achieved for the fabricated prototype was only 0.95% at −20 °C.