Temperature effects on an InGaP (GaInP) 55Fe X-ray photovoltaic cell

Abstract

This paper investigates the effects of temperature on an InGaP (GaInP) 55Fe X-ray photovoltaic cell prototype for a radioisotope microbattery (also called a nuclear microbattery). An In0.5Ga0.5P p-i-n (5 μm i-layer) mesa photodiode was illuminated by a standard 206 MBq 55Fe radioisotope X-ray source and characterised over the temperature range −20 °C to 100 °C. The electrical power output of the device reached its maximum value of 1.5 pW at a temperature of −20 °C. An open circuit voltage and a short circuit current of 0.82 V and 2.5 pA, respectively, were obtained at −20 °C. While the electrical power output and the open circuit voltage decreased with increasing temperature, an almost flat trend was found for the short circuit current. The cell conversion efficiency decreased from 2.1% at −20 °C to 0.7% at 100 °C.

Energy response characterization of InGaP X-ray detectors

“…The incomplete charge collection noise is also photon energy dependent, whereas the electronic noise is photon energy invariant. The incomplete charge collection noise was found to be negligible at -5 V reverse bias [26], thus the quadratic sum of the Fano noise and the electronic noise, E,…”

“…Despite the desirable attributes of In0.5Ga0.5P, very little work has been carried out on the material in regards to the development of X-ray and -ray detectors. The first In0.5Ga0.5P X-ray detectors were reported by Butera et al [26]; an FWHM at 5.9 keV of 900 eV was achieved with the detectors and preamplifier operating at room temperature. In0.5Ga0.5P X-ray detectors have also been investigated for high temperature X-ray spectroscopy, reporting an energy resolution of 1.27 keV FWHM at 5.9 keV, at 100 °C, and 770 eV FWHM at 5.9 keV, at 20 °C [27].…”

“…Two In0.5Ga0.5P p + -in + circular mesa photodiodes (one with a diameter of 200 m; one with a diameter of 400 m) made from the same material as reported in Ref. [26] [27] were characterized for their response to illumination with X-rays within the energy range 4.95 keV to 21.17 keV. A Mo target X-ray tube and 9 high-purity metal fluorescence foils were used (in turn) to generate characteristic X-ray fluorescence lines which illuminated the detectors.…”

6μm thick AlInP55Fe x-ray photovoltaic and63Ni betavoltaic cells

“…Care must also be taken to ensure that the risk of radiation exposure to the users of microbatteries is minimised, and as A c c e p t e d M a n u s c r i p t such the use of softer X-rays and beta particles is preferred compared with harder X-ray and -rays for that reason. Prototype temperature tolerant X-ray photovoltaic cells have also been reported using GaAs [11], Al0.2Ga0.8As [15], and In0.5Ga0.5P as converter materials [17]. The GaAs 55 Fe Xray photovoltaic cell presented an open circuit voltage and maximum output power as high as 0.3 V and 1 pW, respectively, at -20 [11].…”

“…The poor results obtained for the Al0.2Ga0.8As microbattery system were possibly caused by polarization problems due to the presence of traps in the Al0.2Ga0.8As structure [15]. An open circuit voltage of 0.82 V and a maximum output power of 2.5 pW were instead reported for an In0.5Ga0.5P 55 Fe X-ray photovoltaic cell at -20 °C [17]. GaAs [12,13] and In0.5Ga0.5P [18] photodiodes have also played a crucial role in the development of temperature tolerant betavoltaic cells.…”