We have proposed two types of simple-structure silicon (Si) X-ray detectors with 1.5-mm-thick high-resistivity Si substrates, which are able to be operated at reasonably low negative bias and cooled by Peltier cooling. Since the device structures are simple and the detectors require only one high voltage, the cost of the X-ray detection system can be reduced very much. Moreover, the absorption of cadmium X-ray fluorescence (energy: 23.1 keV) in 1.5-mm-thick Si is approximately 65%, whereas in commercial silicon drift detectors (Si thickness: approximately 0.3 mm), it is approximately 19%. We have simulated the electric potential distribution within the proposed detectors and carried out fundamental experiments towards the realization of the detectors.

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.

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