Study of silicon carbide for X-ray detection and spectroscopy

High temperature GaAs X-ray detectors

“…The dielectric noise of a photodiode X-ray spectrometer arises from any lossy dielectrics at the input of the preamplifier, such as the feedback capacitance, the passivation and packaging of the input JFET, the JFET dielectrics, as well as the detector itself and its packaging. [37][38][39] The known dependency of the dielectric noise on the temperature 34 explained the reduction of the dielectric noise as the temperature decreased for both spectrometers, S1 and S2. Also, the greater dielectric noise of the X-ray spectrometer S2 (with D2, 400 lm diameter device) compared to the spectrometer S1 (with D1, 200 lm diameter device) was attributed to the higher capacitance of D2 compared to D1, since the dielectric noise is directly proportional to the capacitance of the lossy dielectrics.…”

“…This total leakage current includes twice the contribution of the detector leakage current, I R , and the input JFET leakage current. 34,39 The leakage current of the input JFET for the currently reported configuration, where the gate of the JFET is slightly forward biased, 30 equals the drain to gate leakage current, I DG . 34 The total leakage current, i.e., 2(I R þ I DG ), was found to decrease from 409 pA at 80 C to 23 pA at -20 C for S1, and from 828 pA at 80 C to 16 pA at -20 C for S2.…”

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

“…8 As relative to that of GaAs (e GaAs ¼ 4.184 eV 6 0.025 eV). 39 This method was previously used to determine e in SiC 6 and GaAs 39 using a Si reference detector, and in Al 0.8 Ga 0.2 As using a GaAs reference detector. 40 The well characterised 41 GaAs p þ -i-n þ mesa X-ray photodiode (200 lm diameter, 10 lm i layer) structure is shown in Table II.…”

“…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.…”

“…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. 6 Al x Ga 1-x As has received particular attention as a promising alternative for X-ray [14][15][16] and beta particle 17,18 detection; the material can be grown nearly lattice matched to readily available GaAs substrates, and by varying the Al concentration, the bandgap can be adjusted in order to meet specific application needs. The benefits exhibited by Al x Ga 1-x As have led to the extensive study of Al 0.8 Ga 0.2 As (i.e., higher Al composition than the present devices) for X-ray detection, where 200 lm diameter Al 0.8 Ga 0.2 As circular mesa p þ -i-n þ photodiodes with 1 lm i layers were characterised as soft Xray photon counting detectors, with an energy resolution (FWHM) of 1.07 keV at 5.9 keV at room temperature for the best performing diode.…”