Abstract
An AlInP 3 × 3 pixel monolithic array was fabricated from a p+-i-n+ structure wafer (6 μm thick i layer) grown by metalorganic vapour phase epitaxy; each pixel (square mesa photodiode) had an area of 200 μm × 200 μm. The pixels were initially electrically characterized and were then subjected to illumination by X-ray and γ-ray photons of energies ≤88 keV while each of them was in turn coupled to a custom-made, low noise, charge-sensitive preamplifier. The photon counting X-/γ-ray spectroscopic performance of the pixels was investigated by obtaining and analysing 55Fe X-ray, 241Am X-/γ-ray, and 109Cd X-/γ-ray spectra; the energy resolution (Full Width at Half Maximum), when the array and preamplifier were operated at the maximum investigated temperature (100 °C), was 1.54 keV ± 0.08 keV at 5.9 keV, 1.58 keV ± 0.08 keV at 22.16 keV, and 1.57 keV ± 0.08 keV at 59.54 keV. This work sets the agenda for future development of an AlInP photon counting X-/γ-ray spectroscopic imager for uncooled operation in high temperature environments.
Highlights
X-ray and γ-ray spectroscopic imaging is used widely in space science, for example for astrophysical [1] and planetary [2] analysis
Apart from D5 and D7, showed similar leakage currents; they ranged from 0.97 pA ± 0.01 pA (D1) to 11.33 pA ± 0.06 pA (D3) at −200 V applied reverse bias
A monolithic AlInP 3 × 3 pixel array detector was explored in photon counting X-ray and γ-ray spectroscopy, while it was operated uncooled at temperatures ≤100 ◦C
Summary
X-ray and γ-ray spectroscopic imaging is used widely in space science, for example for astrophysical [1] and planetary [2] analysis. Other wide bandgap semiconductor detectors shown to be suitable for photon counting X-/γ-ray spectroscopy include Al0.52In0.48P [19], In0.5Ga0.5P [20], 4H-SiC [21], and diamond [22], of which Al0.52In0.48P and In0.5Ga0.5P benefit from high atomic number. Single pixel Al0.52In0.48P circular mesa p+-i-n+ photodiodes with 2 μm and 6 μm thick i layers have been reported to detect spectroscopically 5.9 keV X-ray photons at temperatures up to 100 ◦C [19,26] and they have been investigated for their photon counting X-ray spectroscopic performance within the photon energy range 4.95 keV to 21.17 keV at more modest temperatures [27,28].
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