Speaker
Description
This work presents the results of performance studies conducted on 1.5 mm thick cadmium zinc telluride (CZT) detector structures with differing electrode configurations. The aim was to gain a better understanding of the correlation between the physical processes and the electrical and spectroscopic properties of the studied devices. We performed current-voltage (IV) and capacitance-voltage (CV) measurements, as well as gamma and alpha spectroscopies for multiple CZT samples. To increase the signal-to-noise ratio and get an estimation of the absorbed energy of the radiation sources, we designed the detector enclosure with a built-in collimator 1 mm in diameter.
This suite of measurements yields parameters required to assess the depletion behavior, bulk resistivity, charge collection efficiency, and energy resolution for characteristic peaks of different energies. We observed a correlation between spatial variations in charge induction and non-uniformities of the electric field through the detector response to Am-241, Ba-133, and Cs-137 isotopes emitting gamma and x-ray radiation. Varying the potential difference between the electrodes and irradiating the sample with alpha emissions provides insight into mobility-lifetime characteristics, as well as charge transport and trapping mechanisms within the bulk. The role of defect density across the semiconductor bulk of the measured structures is being investigated in an adjacent study and is yet to be formulated.
The inter-peak distance differences relative to peak centroids and energy resolution of the peaks were used as metrics of performance for alpha spectroscopy. Physical properties of electrical contact interfaces and the external signal path toward the amplifying electronics have a defining influence on signal formation.
To summarize, the results highlight the impact of undesired effects on energy resolution and the performance of CZT-based structures for gamma and alpha detection. This is relevant to the global goal of developing room-temperature, well-performing, high-Z semiconductor devices.
| Workshop topics | Sensor materials, device processing & technologies |
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