13 research outputs found
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Wide bandgap semiconductor radiation detectors for extreme environments
Wide bandgap semiconductor photodiodes were investigated for their suitability as radiation detectors for high temperature applications (≥ 20 °C), through measurements, calculations of key parameters of the devices, and relating the results back to the material, geometry of the detectors, environment under which the detectors were investigated, and previously published work. Three families of photodiodes were examined.
4H-SiC vertical Schottky UV photodiodes with Ni2Si interdigitated contacts were characterised for their response under dark and UV illumination. Electrical characterisation up to 120 °C and room temperature responsivity measurements (210 nm to 380 nm) suggested that the devices could operate at low UV light intensities, even at high visible and IR backgrounds without the use of filters, and at high temperatures.
4H-SiC Schottky photodiode detector arrays with planar thin NiSi contacts were investigated for X-ray (≤ 35 keV) detection and photon counting spectroscopy at 33 °C. The electrical characterisation of the devices up to 140 °C and subsequent analysis suggested that the devices are likely to operate as high temperature X-ray spectrometers.
Results characterising GaAs p+-i-n+ mesa photodiode detectors for their room temperature visible and near infrared responsivity (580 nm to 870 nm), as well as their high temperature (≤ 60 °C) X-ray detection performance (at 5.9 keV) are presented. GaAs p+-i-n+ mesa photodiodes were also shown to be suitable for β- particle (electron) spectroscopy and X-ray fluorescence spectroscopy (≤ 21 keV) at 33 °C.
The X-ray and electron spectroscopic measurements were supported by a comprehensive treatment of the noise components in charge sensitive preamplifiers. Calculations showed the potential benefits of using a SiC, rather than Si, JFET as the input transistor of such a preamplifier operating at high temperatures. The spectroscopic measurements, using both the 4H-SiC and GaAs photodiodes, are presented along with noise analysis to detangle the different noise components present in the reported spectrometers, identify the dominant source of noise, and suggest potential improvements for future spectrometers using the reported devices
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Dataset for research paper: GaAs Spectrometer for Planetary Electron Spectroscopy
Data for 9 figures in research paper appearing in the Journal of Geophysical Research – Space Physics.Figure 2. Measured capacitance of the GaAs p+-i-n+ mesa photodiode within the temperature range 100 °C to 20 °C.Figure 3. Calculated depletion width of the GaAs p+-i-n+ mesa photodiode at 100 °C (filled triangles) and 20 °C (filled circles).Figure 4. Leakage current as a function of applied reverse bias of the GaAs p+-i-n+ mesa photodiode in the temperature range 100 °C down to 20 °C.Figure 5. Quantum detection efficiency, QE, of the detector for electrons of each energy, in detector regions covered by top contacts (diamonds) and not covered by top contacts (circles) as a function of incident electron energy. The weighted quantum efficiency is also shown (open squares).Figure 6. Simulated 63Ni β‑ particle spectrum as emitted from the source (solid line), and incident on the top face of the detector (square dots).Figure 8. Experimentally measured 63Ni β- particle spectra (counts per 1 keV as a function of energy) within the investigated temperature range (between 100 °C and 20 °C, with 20 °C decrements).Figure 9. Comparison between the accumulated 63Ni β- particle spectrum at 20 °C (grey solid line) and the predicted to be detected spectrum (black dashes). The spectrum incident on the detector as calculated with CASINO simulations is also shown.Figure 10. Omnidirectional electron flux expected at Europa (9.5 RJ) as a function of energy, after Paranicas et al. (2009).Figure 11. Comparison between the predicted to be incident on detector (solid line) and to be detected (black dashes) electron spectra (10 keV to 100 keV) of the radiation environment near Europa’s orbit. Electron energy losses within the top contact, the p+ layer, and the n+ layer/substrate explained the difference between the spectra predicted to be incident and predicted to be detected.Abstract from research paper Work towards producing a radiation-hard and high temperature
tolerant direct detection electron spectrometer is reported. The motivation is
to develop a low-mass, low-volume, low-power, multi-mission capable instrument
for future space science missions. The resultant prototype electron
spectrometer employed a GaAs p+-i-n+ mesa photodiode (10
µm i layer thickness; 200 μm diameter) and a custom-made charge-sensitive
preamplifier. The GaAs detector was initially electrically characterized as a
function of temperature. The detector-preamplifier assembly was then
investigated for its utility in electron spectroscopy across the temperature
range 100 °C to 20 °C using a laboratory 63Ni radioisotope β-
particle source (end point energy = 66 keV). Monte Carlo simulations using the
computer program CASINO were conducted and showed that the spectrometer had a
quantum detection efficiency which increased with increasing electron energy up
to 70 keV; a quantum detection efficiency of 73 % was calculated. The
accumulated 63Ni β- particle spectra together with CASINO
simulations of the detected spectra showed that the GaAs based spectrometer could
be used for counting electrons and measuring the energy deposited per electron
in the detector’s active region (i layer). The development of a GaAs electron
spectrometer of this type may find use in future space missions to environments
of intense radiation (such as at the surface of Europa for investigation of
electron-driven radiolysis of ice) and high temperature (such as at Mercury,
and comets passing close to the Sun).</div
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High temperature (= 160 °C) X-ray and ß- particle diamond detector
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Hard X-ray and ?-ray spectroscopy at high temperatures using a COTS SiC photodiode
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AlInP photodiode x-ray detectors
Four Al0.52In0.48P p+-i-n+ mesa photodiodes with 6 µm thick i layers and two different diameters (217 µm??±??15 µm and 409 µm??±??28 µm) were studied at room temperature (24 °C). Electrical characterisation measurements are reported along with measurements showing the performance of the devices as x-ray detectors. The devices exhibited leakage currents??<3 pA (corresponding to leakage current densities??<2 nA cm-2) at 100 V reverse bias (electric field strength of 167?kV cm-1). The photodiodes were coupled to a custom-made low-noise charge-sensitive preamplifier, the noise characteristics of the resultant spectrometers were investigated as functions of shaping times. The best energy resolutions (full width at half maximum of the 5.9?keV photopeak from an 55Fe radioisotope x-ray source) achieved with the 217 µm??±??15 µm and 409 µm??±??28 µm diameter photodiodes were 0.89?keV and 1.05?keV, respectively. The dielectric dissipation factor of Al0.52In0.48P was estimated to be (2.2??±??1.1)??×??10-3 at room temperature
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AlGaAs two by two pixel detector for electron spectroscopy in space environments
A prototype monolithic 2 × 2 square pixel Al0.2Ga0.8As p+ -i-n+mesa photodiode array (each photodiode of area 200 µm by 200 µm, with a 3 µm i layer) has been investigated for its utility as a detector for direct detection electron (ß-particle) spectroscopy. Each photodiode was electrically characterised and its response to illumination from a 63Ni radioisotope ß particle source was investigated at 20 °C. The percentage of electron energy absorbed in the active layer (i layer), Eabs, of the photodiode and the spectrum expected to be detected, were calculated via Monte Carlo simulations. Comparisons between the simulated and detected 63Ni ß particle spectra are presented and demonstrate uniformity in response across the two by two pixel array. The percentage of electron energy absorbed in the active layer of the detector was at a maximum of 0.53 ± 0.04 for electrons with an energy of 38 keV; the percentage of electron energy absorbed in the active layer of the detector reduced to 0.29 ± 0.02 at 66 keV
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GaAs spectrometer for planetary electron spectroscopy
Work towards producing a radiation-hard and high temperature tolerant direct detection electron spectrometer is reported. The motivation is to develop a low-mass, low-volume, low-power, multi-mission capable instrument for future space science missions. The resultant prototype electron spectrometer employed a GaAs p+-i-n+ mesa photodiode (10 µm i layer thickness; ß00 µm diameter) and a custom-made charge-sensitive preamplifier. The GaAs detector was initially electrically characterized as a function of temperature. The detector-preamplifier assembly was then investigated for its utility in electron spectroscopy across the temperature range 100 °C to 20 °C using a laboratory 63Ni radioisotope ?- particle source (end point energy = 66 keV). Monte Carlo simulations using the computer program CASINO were conducted and showed that the spectrometer had a quantum detection efficiency which increased with increasing electron energy up to 70 keV; a quantum detection efficiency of 73 % was calculated. The accumulated 63Ni ?- particle spectra together with CASINO simulations of the detected spectra showed that the GaAs based spectrometer could be used for counting electrons and measuring the energy deposited per electron in the detector’s active region (i layer). The development of a GaAs electron spectrometer of this type may find use in future space missions to environments of intense radiation (such as at the surface of Europa for investigation of electron-driven radiolysis of ice) and high temperature (such as at Mercury, and comets passing close to the Sun)
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Electron spectroscopy with a commercial 4H-SiC photodiode
A Commercial-Off-The-Shelf (COTS) 4H-SiC p-n photodiode (sold as a UV detector) was investigated as detector of electrons (ß- particles) over the temperature range 100 °C to 20 °C. The photodiode had an active area of 0.06 mm2. The currents of the photodiode were measured in dark condition and under the illumination of a 63Ni radioisotope ß- particle source (endpoint energy = 66 keV). The photodiode was then coupled to a custom-made low-noise charge-sensitive preamplifier to make a direct detection particle counting electron spectrometer. 63Ni ß- particle spectra were accumulated with the spectrometer operating at temperatures up to 100 °C. The quantum efficiency of the photodiode as well as the spectrum expected to be detected were calculated via Monte Carlo simulations produced using the CASINO computer program. Comparisons between the simulated and detected 63Ni ß- particle spectra are presented. The work was motivated by efforts to apply COTS technologies to develop low-cost space science instrumentation; a low-cost electron spectrometer of this type could be included on a university-led CubeSat mission for space plasma physics and magnetosphere experiments
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AlInP X-ray photodiodes without incomplete charge collection noise
Previously, an Al0.52In0.48P p+-i-n+ spectroscopic photon counting X-ray photodiode with 2 µm thick i layer (200 µm diameter) was shown to suffer from energy-dependent incomplete charge collection noise [Lioliou et al., 2019, Nucl. Instr. and Meth. A Vol. 943, Art. No. 162467]. Subsequent measurements on a larger (400 µm diameter) Al0.52In0.48P p+ -i-n+ photodiode (reported here) revealed the presence of even greater incomplete charge collection noise. Given these findings, an expectation would have been that thicker Al0.52In0.48P structures (which would be required for efficient absorption of all but the softest X-rays) would have a greater incomplete charge collection noise contribution, thus suggesting that thick Al0.52In0.48P photodiodes may be of limited practicality as high performance detectors for photon counting X-ray spectroscopy. However, two new Al0.52In0.48P p+ -i-n+ photodiodes (with 6 µm i layers) were fabricated from material grown by the same technique (metalorganic vapour phase epitaxy) in the same reactor, and are now shown here to exhibit no signs of detectable incomplete charge collection noise under the illumination of X-ray photons of energy 4.95 keV to 21.17 keV. As such, now that greater experience has been built with Al0.52In0.48P, concerns about incomplete charge collection noise in X-ray detectors made from the material appear to have been unwarranted; the path towards thick Al0.52In0.48P X-ray detectors is now clear
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High temperature AlInP X-ray spectrometers
Two custom-made Al0.52In0.48P p+-i-n+ mesa photodiodes with different diameters (217 µm ± 15 µm and 409 µm ± 28 µm) and i layer thicknesses of 6 µm have been electrically characterised over the temperature range 0 °C to 100 °C. Each photodiode was then investigated as a high-temperature-tolerant photon counting X-ray detector by connecting it to a custom-made low-noise charge-sensitive preamplifier and illuminating it with an 55Fe radioisotope X-ray source (Mn Ka = 5.9 keV; Mn Kß = 6.49 keV). At 100 °C, the best energy resolutions (full width at half maximum at 5.9 keV) achieved using the 217 µm ± 15 µm diameter photodiode and the 409 µm ±28 µm diameter photodiode were 1.31 keV ± 0.04 keV and 1.64 keV ±0.08 keV, respectively. Noise analysis of the system is presented. The dielectric dissipation factor of Al0.52In0.48P was estimated as a function of temperature, up to 100 °C. The results show the performance of the thickest Al0.52In0.48P X-ray detectors so far reported at high temperature. The work has relevance for the development of novel space science instrumentation for use in hot space environments and extreme terrestrial applications