Search

Polarization poses a significant challenge in cadmium telluride (CdTe) detectors, preventing the simultaneous achievement of high energy resolution and long-term stability at room temperature. The mechanism driving bias-induced polarization is presumed to involve an increase in the number of ionized acceptors resulting from hole detrapping. Simultaneously, the accumulation of negative charges is suppressed as the hole density in the bulk increases. Consequently, polarization effects occur in diode-type detectors with low current densities but not in ohmic detectors with high current densities. In this study, we fabricated a diode-type detector with a high current density, which is between those of the ohmic and diode types, and evaluated its long-term stability. The detector had dimensions of 3 × 3 × 0.75 mm³, comprising a central electrode of 0.5 × 0.5 mm² surrounded by a guard-ring electrode. By finely patterning the anode, we increased the current density, achieving a current density comparable to that of the ohmic type while enabling the application of a higher bias voltage. [ABSTRACT FROM AUTHOR]

Cadmium telluride (CdTe) is used as an X-ray image detector for dental applications. However, it is difficult to fabricate the large CdTe chips for such applications. Therefore, it is necessary to increase the detection area by tiling. In this study, to minimize the dead space caused by bonding CdTe and application-specific integrated circuits (ASICs), the detector was three-dimensionally stacked by flip-chip bonding. Furthermore, to achieve a high spatial resolution, a diode-type detector that can apply a high electric field was used. However, in flipchip bonding, layers were stacked while applying pressure and heat; therefore, Schottky-type detectors, which are diode-type detectors, were expected to have a low breakdown voltage because the Schottky junction was located at the interface between the CdTe layer and the electrode. However, the p-n junction was expected to have a high voltage resistance because it was located inside the CdTe layer. Therefore, we performed pressure tests on Schottky-type and p-n junction CdTe detectors, and the I-V and gamma-ray spectral characteristics before and after the tests were evaluated. As expected, the Schottky-type detector stopped exhibiting diode characteristics after pressurization, the reverse current increased, and gamma rays could hardly be detected; however, the p-n junction detector maintained its diode characteristics even after pressurization, and the I-V characteristics indicated a high voltage resistance with almost no change in both the I-V and the gamma-ray spectral characteristics. [ABSTRACT FROM AUTHOR]

The significance of X-ray spectral information is steadily growing. However, pile-up is becoming a pertinent problem at high dosage levels. Additionally, attempts to mitigate pile-up by reducing the surface area of the detector result in charge sharing, making accurate spectrum determination complicated. When materials such as cadmium telluride are employed as detectors, a significant disparity in the mobility of electrons and holes can lead to pulses in the opposite direction across multiple electrodes. We propose to identify charge-sharing events by detecting these opposing pulses. We found that eliminating events associated with negative pulses from the spectrum reduced the full width at half maximum of the peak from 15.9 to 14.4 keV. The proposed method improves the accuracy of spectral measurements under high flux to reduce the effect of charge sharing in single-point spectral measurements. [ABSTRACT FROM AUTHOR]