Evaluation of CZT Detector Performance in Alpha and Gamma Spectrometry

TL;DR

The paper addresses how defect configurations in Cadmium Zinc Telluride (CZT) detectors affect spectroscopic performance by delivering a comprehensive baseline characterization using IV, CV, and gamma- and alpha-spectroscopy on five Vertical Gradient Freeze CZT sensors. It employs a CSP/MCA readout chain, energy calibration with $^{133}$Ba and $^{137}$Cs, and mu-tau estimation via the Hecht framework across a range of biases, revealing substantial sample-to-sample variability including an outlier. Key findings include resistivity spanning several orders of magnitude, linear gamma energy calibration with degraded resolution above $100\,$keV due to incomplete energy deposition, and alpha-response sensitivity to surface/near-surface defects; the data also show bias-dependent SE and $\mu\tau$ behavior. The work establishes a reproducible methodology to link defect composition to spectroscopic performance and provides a baseline for guiding CZT crystal growth and detector design, with suggestions for infrared imaging and larger datasets to strengthen defect-performance correlations.

Abstract

Presented is a work on the performance studies of Cadmium Zinc Telluride (CZT) planar detector structures. Current-voltage (IV), capacitance-voltage (CV), and gamma- and alpha-spectroscopy measurements were carried out to provide the essential baseline required for forthcoming defect configuration impact studies on the detector spectroscopy performance. For each tested sensor, spectroscopic responses were recorded with several bias voltages applied. The described suite of measurements provides the parameters needed to evaluate, bulk resistivity, signal efficiency, and energy resolution for characteristic peaks at different energies. Readout configurations and data processing are discussed in related sections.

Figures (7)

• Figure 1: Block diagrams illustrating two different data acquisition setups used. (a) Setup for characteristic peak position - voltage dependence and spectra measurements with gamma radiation sources. (b) Setup for the alpha source spectra and waveform measurements.
• Figure 2: IV curves measured for the samples under positive and negative bias voltages in both directions. The curves are plotted using a logarithmic scale for y-axis. Microscope images of the tested samples show the differences in electrode shape configurations.
• Figure 3: $^{241}\text{Am}$ spectra at 650 V bias with peaks fit with a Gaussian function corresponding to the 59.51 keV emission. A 10 mVpp pulse generator signal is shown as a reference. Low-energy channels compromised by electronic noise are excluded from the analysis.
• Figure 4: Peak position - voltage dependence.
• Figure 5: Alpha radiation spectra measured with samples 2, 4 and 5 at 650 V bias.