Noise analysis of gallium arsenide pixel X-ray detectors coupled to ultra-low noise electronics

Whitaker

Barnett

2017

Two GaAs p þ -i-n þ mesa X-ray photodiodes were characterized for their electrical and photon counting X-ray spectroscopic performance over the temperature range of 100 C to -20 C. The devices had 10 lm thick i layers with different diameters: 200 lm (D1) and 400 lm (D2). The electrical characterization included dark current and capacitance measurements at internal electric field strengths of up to 50 kV/cm. The determined properties of the two devices were compared with previously reported results that were made with a view to informing the future development of photon counting X-ray spectrometers for harsh environments, e.g., X-ray fluorescence spectroscopy of planetary surfaces in high temperature environments. The best energy resolution obtained (Full Width at Half Maximum at 5.9 keV) decreased from 2.00 keV at 100 C to 0.66 keV at -20 C for the spectrometer with D1, and from 2.71 keV at 100 C to 0.71 keV at -20 C for the spectrometer with D2. Dielectric noise was found to be the dominant source of noise in the spectra, apart from at high temperatures and long shaping times, where the main source of photopeak broadening was found to be the white parallel noise.

Section: A Dark Current Measurementsmentioning

confidence: 99%

High temperature GaAs X-ray detectors

Whitaker

Barnett

2017

“…(1) rather than Eq. (2) suggesting that the forward current was defined by the recombination current rather than the diffusion current. More specifically, the same proportionality factor was calculated using Eq.…”

Section: Electrical Characterization a Current Measurementsmentioning

confidence: 99%

“…Other high quality GaAs p-i-n diodes had a leakage current density of $10 nA/cm 2 at the same temperature and internal electric field. 2 …”

Section: Electrical Characterization a Current Measurementsmentioning

confidence: 99%

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Temperature dependent characterization of gallium arsenide X-ray mesa p-i-n photodiodes

Barnett

2016

Electrical characterization of two GaAs p þ -i-n þ mesa X-ray photodiodes over the temperature range 0 C to 120 C together with characterization of one of the diodes as an X-ray detector over the temperature range 0 Ct o6 0 C is reported as part of the development of photon counting X-ray spectroscopic systems for harsh environments. The randomly selected diodes were fully etched and unpassivated. The diodes were 200 lm in diameter and had 7 lm thick i layers. The leakage current density was found to increase from (3 6 1) nA/cm À2 at 0 C to (24.36 6 0.05) lA/ cm À2 at 120 C for D1 and from a current density smaller than the uncertainty (0.2 6 1.2) nA/cm À2 at 0 C to (9.39 6 0.02) lA/cm À2 at 120 C for D2 at the maximum investigated reverse bias (15 V). The best energy resolution (FWHM at 5.9 keV) was achieved at 5 V reverse bias, at each temperature; 730 eV at 0 C, 750 eV at 20 C, 770 eV at 40 C, and 840 eV at 60 C. It was found that the parallel white noise was the main source of the photopeak broadening only when the detector operated at 60 C, at 5 V, 10 V, and 15 V reverse bias and at long shaping times (>5 ls), whereas the sum of the dielectric noise and charge trapping noise was the dominant source of noise for all the other spectra. V C 2016 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4944892]

“…Wide bandgap materials, such as GaAs, [1][2][3][4][5] SiC, [6][7][8] diamond, 9,10 Al 0.52 In 0.48 P, [11][12][13] and Al x Ga 1-x As, [14][15][16] are of interest for use in space science and extreme terrestrial applications where detectors are exposed to high temperatures and intense radiation. Traditional Si X-ray spectrometers often require significant shielding and cooling mechanisms in order to function within extreme environments (e.g., ) 20 C), whereas wide bandgap detectors are more robust and can possess superior energy resolution at high temperatures due to lower thermally induced leakage currents.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of Al0.2Ga0.8As X-ray photodiodes for X-ray spectroscopy

Whitaker

Butera

et al. 2017

Two custom-made Al0.2Ga0.8As p+-i-n+ mesa X-ray photodiodes (200 μm diameter, 3 μm i layer) have been electrically characterised across the temperature range −20 °C to 60 °C. The devices were connected to a custom-made charge sensitive preamplifier to produce an AlGaAs photon-counting X-ray spectrometer. The devices' responses to illumination with soft X-rays from an 55Fe radioisotope X-ray source (Mn Kα = 5.9 keV; Mn Kβ = 6.49 keV) were investigated across the temperature range −20 °C to 20 °C. The best energy resolution (FWHM at 5.9 keV) achieved at 20 °C was 1.06 keV (with the detector at 10 V reverse bias). Improved FWHM was observed with the devices at temperatures of 0 °C (0.86 keV) and −20 °C (0.83 keV) with the photodiode reverse biased at 30 V. The average electron hole pair creation energy was experimentally measured and determined to be 4.43 eV ± 0.09 eV at 20 °C, 4.44 eV ± 0.10 eV at 0 °C, and 4.56 eV ± 0.10 eV at −20 °C.