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CdZnTe (CZT) is a very promising material for nuclear-radiation detectors. CZT detectors operate at ambient
temperatures and offer high detection efficiency and excellent energy resolution, placing them ahead of high-purity Ge
for those applications where cryogenic cooling is problematic. The progress achieved in CZT detectors over the past
decade is founded on the developments of robust detector designs and readout electronics, both of which helped to
overcome the effects of carrier trapping.
Because the holes have low mobility, only electrons can be used to generate signals in thick CZT detectors, so one must
account for the variation of the output signal versus the locations of the interaction points. To obtain high spectral
resolution, the detector's design should provide a means to eliminate this dependence throughout the entire volume of
the device. In reality, the sensitive volume of any ionization detector invariably has two regions. In the first, adjacent to
the collecting electrode, the amplitude of the output signal rapidly increases almost to its maximum as the interaction
point is located farther from the anode; in the rest of the volume, the output signal remains nearly constant. Thus, the
quality of CZT detector designs can be characterized based on the magnitude of the signals variations in the drift region
and the ratio between the volumes of the drift and induction regions. The former determines the "geometrical" width of
the photopeak, i.e., the line width that affects the total energy resolution and is attributed to the device's geometry when
all other factors are neglected. The latter determines the photopeak efficiency and the area under the continuum in the
pulse-height spectra.
In this work, we describe our findings from systematizing different designs of CZT detectors and evaluating their
performance based on these two criteria.
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