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Open Electrical & Electronic Engineering Journal;2013, Vol. 7, p1.
Hideharu Matsuura, , Derek Hullinger, and Keith W. Decker.
Osaka Electro-Communication University, 18-8 Hatsu-cho, Neyagawa, Osaka 572-8530, Japan and
MOXTEK, Inc., 452 West 1260 North, Orem, UT 84057, USA
Abstract
A proposed simply structured gated silicon (Si) drift X-ray detector operated using Peltier cooling and only a single high-voltage source is investigated. Because the device structure is much simpler than that of commercial Si drift detectors (SDDs), which require at least two high-voltage sources, the cost of the X-ray detection system can be reduced. The absorption of cadmium X-ray fluorescence photons (energy: 23.1 keV) in 0.3-mm-thick Si is only 19% in commercial SDDs. Toward realizing detectors with thicker Si substrates, we simulate the electric potential distribution in the proposed detector with a Si substrate having thickness of 0.625 mm and resistivity of 10 kΩ·cm, and we perform fundamental experiments on a fabricated prototype. The simulation result is in good agreement with the experimental result that the effective active area of the detector is approximately 18 mm² by using incident X-rays passed through a 0.1-mm-diameter pinhole. An energy resolution of 145 eV at 5.9 keV is experimentally obtained from an 55Fe source at -38 °C.
Additional information:
GSDD has the advantage ofbeing (1) a simple structure, (2) a single high-voltage source, (3) applicable to thicker Si, and (4) applicable to higher Si resistivity, compared with SDD, as well as (5) operated at a reverse bias much lower than that inSi pin detectors.
The SDDfabricated using the Si resistivity higher than 2 kΩ·cm (the resistivity of commercial SDD), unfortunately, behaved as a pnp transistor with the p ring as an emitter, the anode as a base, and the cathode as a collector, indicating that the current between the p-ring and the cathode depends on the anode current and becomes much large. However, GSDD can be normally operated even in the case that higher Si resistivity is used. These findings are reported in Key Engineering Materials Vol. 495 (2012) pp 294-297.
In GSDD with an active area of 18mm2 and a 10-kΩ·cm Si thickness of 1.5 mm, a GSDD gate pattern was designed for various oxide charge densities in the SiO2passivating layer near the SiO2/Si interface. The simulated GSDDs required approximately half the reverse bias voltage required by Si pin detectors. Our detector design could improve the absorption of Cd X-ray fluorescence photons (approximately 65%) and would reduce the cost of X-ray detection systemsroughly by one-tenth. These findings are reported in Japanese Journal of Applied Physics 52 (2013) 024301.
