Gallium arsenide 55Fe X-ray-photovoltaic battery

Abstract

The effects of temperature on the key parameters of a prototype GaAs 55Fe radioisotope X-ray microbattery were studied over the temperature range of −20 °C to 70 °C. A p-i-n GaAs structure was used to collect the photons from a 254 Bq 55Fe radioisotope X-ray source. Experimental results showed that the open circuit voltage and the short circuit current decreased with increased temperature. The maximum output power and the conversion efficiency of the device decreased at higher temperatures. For the reported microbattery, the highest maximum output power (1 pW, corresponding to 0.4 μW/Ci) was observed at −20 °C. A conversion efficiency of 9% was measured at −20 °C.

AlGaAs 55Fe X-ray radioisotope microbattery

“…3, the open circuit voltage ( V OC ) decreased with temperature in the studied Al 0.2 Ga 0.8 As devices. The observed values of open circuit voltage of the presently reported microbattery were lower than those of the previously reported GaAs13 and Al 0.52 In 0.48 P14 55 Fe radioisotope microbatteries. At −20 °C, for example, the Al 0.2 Ga 0.8 As 55 Fe radioisotope microbattery had a V OC of 0.2 V; whilst the GaAs and Al 0.52 In 0.48 P microbatteries had V OC of 0.3 V and 1 V, respectively.…”

“…2, an almost flat trend was observed for the short circuit current with temperature; this was possibly due to the increased optical (X-ray) carrier generation being compensated by the decrease in the carrier diffusion lengths when the temperature was increased. The values of short circuit current observed for the Al 0.2 Ga 0.8 As 55 Fe radioisotope microbattery were much lower than that previously reported for GaAs (~7 pA at −20 °C)13 and Al 0.52 In 0.48 P (~1.15 pA at −20 °C)14 55 Fe radioisotope microbatteries. This smaller short circuit current in the presently reported Al 0.2 Ga 0.8 As microbattery was mainly attributed to the poorer crystalline quality of the Al 0.2 Ga 0.8 As structure with respect to the GaAs and Al 0.52 In 0.48 P detectors.…”

“…This makes their use possible in harsh environment conditions and reduces the likelihood of radiation damage from the integrated radioisotope or from external radiation sources. Recently, multiple types of nuclear microbattery have been reported7891011121314. Diamond detectors were investigated by Bormashov et al 7.…”

“…0.3 μW·g·Ci −1 ·cm −2 for the beta emitter 147 Pm1). However, recently, the electron capture X-ray emitter 55 Fe (0.017 μW·g·Ci −1 ·cm −2  1) has received research attention for nuclear microbattery use1314. Butera et al .…”

“…Butera et al . reported temperature dependent characterisation of different types of 55 Fe radioisotope X-ray microbatteries using GaAs and Al 0.52 In 0.58 P p + -i-n + photodiodes as conversion devices1314: at −20 °C (the lowest temperature investigated and the temperature at which the devices had the best performance) the 55 Fe-GaAs microbattery and the 55 Fe-Al 0.52 In 0.58 P microbattery had internal conversion efficiencies of 9% and 22%, respectively. Although 55 Fe has a lower energy per Curie compared to other candidate radioisotope sources, its use is attractive because of the reduced damage risk for the converter device due to the low energy photons emitted.…”