CdTe Detectors Research Articles

Comparison of the performance and energy resolution of CdTe and Si detectors in the X-ray Fluorescence studies of metal samples and Alloys

X-ray fluorescence provides a powerful means of non-destructively determining the elemental composition of a sample. X-rays from a Molybdenum (Mo) source was fired on copper, molybdenum, lead, steel and brass samples to determine their composition and relative abundance of their constituent elements. Two different detectors: the Cadmium Telluride (CdTe) and Silicon(Si) detectors were used to pick up the signals from the scattering of the X-rays at the sample surfaces and their energy resolutions as well as efficiencies were compared. With a non-noisy amplifier, the Si detector had a higher resolution (0.27 % ) when compared to the 0.38 % for the CdTe detector but it had a lower efficiency when compared to that of the CdTe detector. It was also discovered that higher energies produced lower detector efficiencies.

First light of MC[formula omitted]-1K, a 250 [formula omitted]m pixel pitch CdTe imaging spectrometer for hard X-ray astronomy

The next generation of hard X-ray space telescopes for astrophysics and solar physics requires the development of focal planes with high detection efficiency above 10 keV and enhanced spectroscopic imaging performance. We designed and produced MC2-1K, the first prototype of a new family of fine pitch hybrid detectors. It consists of a 32 × 32 pixel CdTe semiconductor detector point-to-point connected to the spectroscopic channels of a full-custom ASIC. The ASIC named D2R2 was produced in 2019 in the XFAB 0.18 μm technology and has the same 250 μm pixel pitch as the detector. We demonstrated a median equivalent charge noise of 54 e- RMS, equivalent to an energy resolution of 654 eV at 31 keV for a CdTe detector. We developed an acquisition system where the signals of D2R2’s 32 rows are encoded in parallel by a 32-channel ADC ASIC, OWB-1. The custom daughter board with the hybrid detector is placed in a thermally controlled vacuum chamber for a moderate cooling. This paper will present the characterization tests of the ASIC, the dedicated test set-up and the first spectroscopic measurements of the MC2-1K hybrid detector.

Spectroscopic X-ray imaging at MHz frame rates — the HEXITECMHz ASIC

The HEXITECMHz ASIC has been developed for the HEXITECMHz Detector System, to deliver spectroscopic x-ray imaging at frame rates up to 1 MHz for future high-flux-rate applications. Optimised for sensing electron signals from detector materials such as CdTe, CdZnTe, GaAs and p-type silicon detectors, the design has an array of 80 × 80 pixels on a pitch of 250 μm, with each pixel capable of measuring single x-ray photons up to energies of 300 keV, with a resolution of 1 keV FWHM. The induced charge signals that are measured by the ASIC will typically be due to the drift of electrons in the sensor material. However, each pixel is also capable of measuring signals of the opposite polarity with magnitudes of up to 20 keV. These events are induced by weighting potential crosstalk and trapping in the sensor and can be exploited in order to provide further improvements in the spatial and spectroscopic performance of the detector. The signals from pixels are digitized every 1 μs by 12-bit time-to-digital converters. This gives a maximum of 107 photons s−1 mm−2 that can be measured. However, for spectroscopic imaging the occupancy should be limited to 10% in each frame to reduce the charge sharing events. This gives a count rate limit of 106 photons s−1 mm−2 which is two orders of magnitude greater than the previous HEXITEC ASICs. To save power, each converter is shared between groups of eight pixels. Each 76.8 kbit data frame is Aurora 64b/66b encoded and serialised over 20 lanes of differential CML, all operating in parallel at 4.1 Gbps. The ASIC can free run with an asynchronous source or can be synchronized with a pulsed source using the SYNC control input. Expected power consumption is 12–15 W from a 1.8 V supply.

A SIMIND Monte Carlo Simulation Study on CdTe and NaI (Tl) Thickness as Detectors of a Small Animal SPECT System

Purpose: Micro Single Photon Emission Computed Tomography (Micro-SPECT) system has recently been introduced on nuclear medicine in the preclinical and research in which NaI (Tl) and Cadmium Telluride (CdTe) are used as the gamma-ray detectors with more generally use of NaI (Tl). The present study aimed to evaluate different thicknesses of the NaI (Tl) and (CdTe) detectors on functional parameters of a micro-SPECT system.
 Materials and Methods: A Micro-SPECT system with CdTe semiconductor detector and a hexagonal parallel hole collimator with a hole diameter of 0.11 mm, high of 24.05 mm, and septal thickness of 0.016 mm was simulated by Simulating Medical Imaging Nuclear Detectors (SIMIND) Monte Carlo program. The system performance was assessed by comparing the functional parameters, including system efficiency, sensitivity, energy and spatial resolution with the NaI (Tl) detector. The simulated scans of a 99mTc point source, a digital micro-Jacszack phantom, and a voxelized MOBY mouse phantom with the system were prepared to evaluate image quality.
 Results: The functional parameters; sensitivity, efficiency, planar spatial resolution, and image contrast of CdTe detector were determined 1.4, 1.2, 1.7, and 1.8 times higher than those of NaI (Tl), respectively. Moreover, the calculated energy resolution of CdTe and NaI (Tl) detectors was obtained 6.2% and 10.2% at 141 KeV, respectively. In the filtered back projection (FBP) reconstructed images of the micro-Jacszack phantom, minimum detectable size of the cold rods with CdTe and NaI (Tl) detectors were obtained 0.79 mm and 0.95 mm, respectively.
 Conclusion: The imaging system with a 5.5 mm thickness CdTe detector provided better image quality and showed considerable efficiency.

Low-Temperature Annealing of CdTe Detectors With Evaporated Gold Contacts and Its Effect on Detector Performance

Cadmium telluride (CdTe) detectors are usually subjected to elevated temperatures during postprocessing and bonding them to readout electronics while fabricating imaging arrays. We studied the effects of low-temperature and short duration rapid thermal annealing of CdTe bulk as well as CdTe epitaxial-layer-based detectors with evaporated gold contacts. The detectors were annealed in the temperature range of 100 °C–300 °C, and its effect on the detector dark current, gamma detection property, and response stability was studied. For the bulk-detectors, the detector dark current decreased and gamma detection properties as well as the performance stability improved after annealing. However, such improvements were moderate for epitaxial-layer-based detectors. The study of the metal–semiconductor interface of annealed detectors revealed that diffused gold, elemental oxygen, and tellurium oxide existed and extended deep inside the bulk portion in epitaxial detectors; however, they were confined in the surface regions only in bulk-detectors, which likely be the causes of observed results in these two types of detectors.

Experimental characterization of an X-ray photon counting detector

This paper presents the experimental test results of the X-ray photon counting detectors based on our pixel readout ASIC. The chip integrates a 64 × 128 array of pixels in the size of 150 µm × 150 µm and each pixel consists of four 12-bit energy windows. Two types of CdTe detectors have been bump bonded to the ASICs and have been tested.The electronic characteristics of the readout chip were evaluated first by injecting charge through the calibration capacitors. The non-uniformity of the energy thresholds among pixels was measured and then were compensated by tuning the local DACs.The detector performance was then characterized using X-ray tubes. The energy responses of the detectors were measured using the characteristic X-ray of the target materials. The global energy thresholds were then calibrated with these specific energies of photons. Polarization effects under different photon fluxes were also studied. Preliminary imaging was conducted. The detector response under uniform irradiation was investigated. The spatial uniformity of the detectors was analyzed and the flat field correction was then conducted to improve image quality. CT detailed test results will be discussed in this paper.

Коррекция аппаратурного спектра CdTe-детектора в области рентгеновского излучения с граничной энергией до 150 кэВ

The article devotes to algorithm for the instrumental spectrum correction of a CdTe detector in the low-energy X-ray region with a cutoff energy < 150 keV. By minimizing the influence of the detector’s response function, the algorithm allows the instrumental spectrum to be reconstructed, approaching its shape closer to the true one. Particular attention is paid to the low-energy region with the boundary energy up to 100 keV. For a given region, the algorithm makes it possible to correct the spectrum taking into account the difference between the theoretical efficiency curve and the modeled efficiency curve. The main goal of developing an improved algorithm is to determine the characteristics of the radiation quality of an X-ray facility.

Application of adversarial learning for identification of radionuclides in gamma-ray spectra

The rapid and accurate identification of radionuclides brings crucial information for nuclear monitoring to diagnose unknown radiological scenes. Recent studies have used a deep learning approach based on neural networks to develop algorithms that perform well in terms of accuracy and computation time and can also identify radionuclides with a limited number of photons. However, it has been shown that conventional neural networks are not necessarily robust, in the sense that a small particular perturbation of the input data can mislead the networks. A specific learning procedure is necessary to overcome this lack of robustness. In this paper, we show that small perturbations intentionally injected into gamma-ray spectra, with respect to the Poisson statistics, are able to fool the network. We propose applying a robust learning procedure, called “adversarial learning”. We evaluate this procedure using a CdTe detector, namely Caliste-HD. We train a Convolutional Neural Network (CNN) with a synthetic database composed of simulated spectra and we test its performance on real data acquired with a Caliste detector.

Current drive experiments in SST1 tokamak with lower hybrid waves

The steadystate superconducting tokamak (SST1) is aimed to demonstrate long pulse plasma discharges employing non-inductive current drive by means of lower hybrid current drive (LHCD) system. The major and minor radius of the machine is 1.1 m and 0.2 m, respectively. The LHCD system for SST1 comprises of klystrons, each rated for 0.5 MW-CW rf power at a frequency of 3.7 GHz. The grill antenna comprises of two rows, each row accommodating 32 waveguide elements. Electron cyclotron resonance breakdown assisted Ohmic plasma is formed in SST1 to overcome the issues associated with low loop voltage start-ups. With recent modifications in the poloidal coils configuration, even with narrow EC pulse (∼50 ms), good repeatable and consistent Ohmic plasmas could be produced which helped in carrying out LHCD current drive experiments on SST1. These experiments demonstrated both fully as well as partially driven non-inductive plasma current in SST1 tokamak. Discharges with zero loop voltages were obtained. The interaction of lower hybrid waves with plasma and generation of suprathermal electrons could be established using energy spectra measured by CdTe detectors. Various other signatures like drop in loop voltages, negative loop voltages, spikes in hard x-rays and increase in second harmonic ECE signal, further confirmed the current drive by LHW’s. The beneficial effect of LHW’s in suppressing hard x-rays was also demonstrated in these experiments. The longest discharge of ∼650 ms could be obtained in SST1 with the help of LHW’s. In this paper, the experimental results obtained with LHCD experiments on SST1 is reported and discussed in more details.

Using Powder Diffraction Patterns to Calibrate the Module Geometry of a Pixel Detector

The precision and accuracy of diffraction measurements with 2D area detectors depends on how well the experimental geometry is known. A method is described to measure the module geometry in order to obtain accurate strain data using a new Eiger2 4M CdTe detector. Smooth Debye–Scherrer powder diffraction rings with excellent signal to noise were collected by using a fine-grained sample of CeO2. From these powder patterns, the different components of the module alignment errors could be observed when the overall detector position was moved. A least squares fitting method was used to refine the detector module and scattering geometry for a series of powder patterns with different beam centers. A precision that is around 1/350 pixel for the module positions was obtained from the fit. This calibration was checked by free refinement of the unit cell of a silicon crystal that gave a maximum residual strain value of 2.1 × 10−5 as the deviation from cubic symmetry.

Use of the Fully Spectroscopic Pixelated Cadmium Telluride Detector for Benchtop X-Ray Fluorescence Computed Tomography.

In this work, we integrated a commercially-available fully-spectroscopic pixelated cadmium telluride (CdTe) detector system as a two-dimensional (2D) array detector into our existing benchtop cone-beam x-ray fluorescence computed tomography (XFCT) system. After integrating this detector, known as High-Energy X-ray Imaging Technology (HEXITEC), we performed quantitative imaging of gold nanoparticle (GNP) distribution in a small animal-sized phantom using our benchtop XFCT system. Owing to the upgraded detector component within our benchtop XFCT system, we were able to conduct this phantom imaging in an unprecedented manner by volumetric XFCT scans followed by XFCT image reconstruction in 3D. The current results showed that adoption of HEXITEC, in conjunction with a custom-made parallel-hole collimator, drastically reduced the XFCT scan time/dose. Compared with the previous work performed with our original benchtop XFCT system adopting a single crystal CdTe detector, the currently observed reduction was up to a factor of 5, while achieving comparable GNP detection limit under similar experimental conditions. Overall, we demonstrated, for the first time to the best our knowledge, the feasibility of benchtop XFCT imaging of small animal-sized objects containing biologically relevant GNP concentrations (on the order of 0.1 mg Au/cm3 or 100 parts-per-million/ppm), with the scan time (on the order of 1 minute)/x-ray dose (on the order of 10 cGy) that are likely meeting the minimum requirements for routine preclinical imaging applications.

Quality assessment of cadmium telluride as a detector material for multispectral medical imaging

Cadmium telluride (CdTe) is a high-Z material with excellent photon radiation absorption properties, making it a promising material to include in radiation detection technologies. However, the brittleness of CdTe crystals as well as their varying concentration of defects necessitate a thorough quality assessment before the complex detector processing procedure. We present our quality assessment of CdTe as a detector material for multispectral medical imaging, a research which is conducted as part of the Consortium Project Multispectral Photon-counting for Medical Imaging and Beam characterization (MPMIB). The aim of the project is to develop novel CdTe detectors and obtain spectrum-per-pixel information that make the distinction between different radiation types and tissues possible. To evaluate the defect density inside the crystals — which can deteriorate the detector performance — we employ infrared microscopy (IRM). Posterior data analysis allows us to visualise the defect distributions as 3D defect maps. Additionally, we investigate front and backside differences of the material with current-voltage (IV) measurements to determine the preferred surface for the pixelisation of the crystal, and perform test measurements with the prototypes to provide feedback for further processing. We present the different parts of our quality assessment chain and will close with first experimental results obtained with one of our prototype photon-counting detectors in a small tomographic setup.

Multi-contrast CT imaging using a high energy resolution CdTe detector and a CZT photon-counting detector

Computed tomography (CT) imaging with high energy resolution detectors shows great promise in material decomposition and multi-contrast imaging. Multi-contrast imaging was studied by imaging a phantom with iodine (I), gadolinium (Gd), and gold (Au) solutions, and mixtures of the three using a cadmium telluride (CdTe) spectrometer with an energy resolution of 1% as well as with a cadmium zinc telluride (CZT) detector with an energy resolution of 13%. The phantom was imaged at 120 kVp and 1.1 mA with 7 mm of aluminum filtration. For the CdTe data collection, the phantom was imaged using a 0.2 mm diameter x-ray beam with 96 ten-second data acquisitions across the phantom at 45 rotation angles. For the CZT detector, we had 720 projections using a cone beam, and the six detector energy thresholds were set to 23, 33, 50, 64, 81, and 120 keV so that three thresholds corresponded to the K-edges of the contrast agents. Contrast agent isolation methods were then examined. K-edge subtraction and novel spectrometric algebraic image reconstruction (SAIR) were used for the CdTe data. K-edge subtraction alone was used for the CZT data. Linearity plots produced similar R 2 values and slopes for all three reconstruction methods. Comparing CdTe methods, SAIR offered less noise than CdTe K-edge subtraction and better geometric accuracy at low contrast concentrations. CdTe contrast agent images of I, Gd, and Au offered less noise and greater contrast than the CZT images, highlighting the benefits of high energy resolution CdTe detectors for possible use in pre-clinical or clinical CT imaging.

Pixel readout IC for CdTe detectors operating in single photon counting mode with interpixel communication

This paper presents a readout integrated circuit (IC) of pixel architecture called MPIX (Multithreshold PIXels), designed for CdTe pixel detectors used in X-ray imaging applications. The MPIX IC area is 9.6 mm × 20.3 mm and it is designed in a CMOS 130 nm process. The IC core is a matrix of 96 × 192 square-shaped pixels of 100 µm pitch. Each pixel contains a fast analog front-end followed by four independently working discriminators and four 12-bit ripple counters. Such pixel architecture allows photon processing one by one and selecting the X-ray photons according to their energy (X-ray colour imaging). To fit the different range of applications the MPIX IC has 8 possible different gain settings, and it can process the X-ray photons of energy up to 154 keV. The MPIX chip is bump-bonded to the CdTe 1.5 mm thick pixel sensor with a pixel pitch of 100 µm. To deal with the charge sharing effect coming from a thick semiconductor pixel sensor, multithreshold pattern recognition algorithm is implemented in the readout IC. The implemented algorithm operates both in the analog domain (to recover the total charge spread between neighboring pixels, when a single X-ray photon hits the border of the pixel) and in the digital domain (to allocate a hit position to a single pixel).

Sensitivity enhancement of an experimental benchtop X-ray fluorescence imaging system by deploying a single crystal cadmium telluride detector system optimized for high flux X-ray operations

In this work, an energy-resolving thermoelectrically cooled single crystal cadmium telluride (CdTe) detector system upgraded with the latest firmware was optimized for high X-ray flux operations using high bias voltage and fast peaking time. This detector system was deployed into an experimental benchtop X-ray fluorescence (XRF) imaging/computed tomography (XFCT) system developed for quantitative imaging of metal nanoprobes such as gold nanoparticles (GNPs). Using the firmware-upgraded and existing/old CdTe detector systems, the Compton/XRF spectra from small (8 mm diameter) GNP-containing phantoms were acquired. The phantoms were irradiated with 1.8 mm Sn-filtered 125 kVp cone beam X-rays at 24 mA. The firmware-upgraded detector system produced relatively lower dead time under high X-ray flux, compared with the old detector system, and performed well with the spectral resolution of ∼0.7 keV (in full width at half maximum) at 69 keV photon energy. Given the same 2 mm aperture detector collimator and irradiation time of 10 s, this detector system managed to score nearly 50% more gold XRF signals than the existing one at all GNP concentrations tested. This improvement resulted in the GNP detection limit of 0.02 wt. % which was lower than that (0.03 wt. %) achievable with the existing detector system. When combined with the detector collimator containing a larger (3 mm) aperture, the firmware-upgraded detector system produced drastically more gold XRF signal at a given GNP concentration (e.g., 9 times more for 1 wt. % GNP solution and irradiation time of 10 s), leading to further reduction in the GNP detection limit (i.e., 0.01 wt. %). The present investigation showed that the firmware upgraded CdTe detector system optimized for high X-ray flux operations allowed for better photon counting efficiency, thus leading to sensitivity enhancement of an experimental benchtop XRF/XFCT imaging system.

Bias-voltage dependent operational characteristics of a fully spectroscopic pixelated cadmium telluride detector system within an experimental benchtop x-ray fluorescence imaging setup

Commercially available fully spectroscopic pixelated cadmium telluride (CdTe) detector systems have been adopted lately for benchtop x-ray fluorescence (XRF) imaging/computed tomography (XFCT) of objects containing metal nanoprobes such as gold nanoparticles (GNPs). To date, however, some important characteristics of such detector systems under typical operating conditions of benchtop XRF/XFCT imaging systems are not well known. One important but poorly studied characteristic is the effect of detector bias-voltage on photon counting efficiency, energy resolution, and the resulting material detection limit. In this work, therefore, we investigated these characteristics for a commercial pixelated detector system adopting a 1-mm-thick CdTe sensor (0.25-mm pixel-pitch), known as HEXITEC, incorporated into an experimental benchtop cone-beam XFCT system with parallel-hole detector collimation. The detector system, operated at different bias-voltages, was used to acquire the gold XRF/Compton spectra from 1.0 wt% GNP-loaded phantom irradiated with 125 kVp x-rays filtered by 1.8-mm Tin. At each bias-voltage, the gold XRF signal, and the full-width-at-half-maximum at gold Kα 2 XRF peak (∼67 keV) provided photon counting efficiency and energy resolution, respectively. Under the current experimental conditions, the detector photon counting efficiency and energy resolution improved with increasing bias-voltage by ∼41 and ∼29% at −300V; ∼54 and ∼35% at −500V, respectively, when compared to those at −100V. Consequently, the GNP detection limit improved by ∼26% at −300V and ∼30% at −500V. Furthermore, the homogeneity of per-pixel energy resolution within the collimated detector area improved by ∼34% at −300V and ∼54% at −500V. These results suggested the gradual improvements in the detector performance with increasing bias-voltage up to −500V. However, at and beyond −550V, there were no discernible improvements in photon counting efficiency and energy resolution. Thus, the bias-voltage range of −500 to −550V was found optimal under the current experimental conditions that are considered typical of benchtop XRF/XFCT imaging tasks.

Measurements of charge sharing in a hybrid pixel photon counting CdTe detector

Hybrid pixel radiation detectors working in a single-photon counting mode have gained increasing attention due to their noiseless imaging and high dynamic range. Due to the fact that sensors of different materials can be attached to the readout circuit, they allow operation with a wide range of photon energies. The performance of the single photon counting detectors is limited by pile-up. To allow a detector to work under high flux conditions, the pixel size is reduced, which minimizes detector dead time. However, with smaller pixel sizes the charge sharing effect, a phenomenon that deteriorates both detection efficiency and spatial resolution is more profound.The influence of charge sharing on the detector performance can be quantified using parameterization of the s-curve obtained in the spectral response measurements. The article presents the measurements of the response function of a hybrid pixelated photon counting detector for certain primary energy, which corresponds to the probability of detecting a photon as a function of its energy deposition. The measurements were carried out using an X-ray tube by performing a threshold scan during illumination with X-ray photons of a 1.5 mm and 0.75 mm thick CdTe detector with 100 µm pixel pitch. The charge size cloud depends on the sensor material, the bias voltage, and the sensor thickness. Therefore, the experimental data from a sensor biased with different bias voltages are compared to the theoretical results based on a cascaded model of a single-photon counting segmented silicon detector. The study of the charge sharing influence on the spatial resolution of the CdTe detector will serve for a further study of the possible implementations of the algorithms achieving subpixel resolution, in which the charge sharing becomes the desired effect since the charge division in the pixels is used to interpolate the photon interaction position.

Applying Energy-Dispersive X-Ray Fluorescence Analysis to Detect Tungsten Inclusions in Nuclear Fuel Rod End Plug TIG Welds

This study proposes a new method of detecting tungsten inclusions in nuclear fuel rod upper-end plug welds using energy-dispersive X-ray fluorescence (EDXRF) analysis. The Monte Carlo simulation method was used to simulate the process of detecting tungsten inclusions in nuclear fuel rod upper-end plug welds by the EDXRF. The detectable tungsten particle diameters in the zirconium alloy at different depths in welds and the detection limits of the trace tungsten dispersed in welds were obtained. Then, we constructed an experimental device that uses a CdTe detector with an X-ray tube. The results showed that the relative standard deviation of the net count rate of tungsten K-series characteristic X-rays [W (Kα)] was 1.46%, and the optimum parameters are a tube voltage of 150 kV and current of 0.5 mA. These values were used to perform energy-dispersive X-ray fluorescence analysis. These results were compared to the X-ray radiographic results, which were broadly similar. Furthermore, the results of EDXRF analysis were more legible and reliable than those from X-ray radiographic inspections. This study demonstrates the feasibility of applying EDXRF analysis to detect tungsten inclusions.

Polarimetry With a Multilayer CdTe Prototype for Soft Gamma-Ray Astrophysics

The development of a new generation of soft gamma-ray telescopes should allow polarimetric measurements of astrophysical sources to be associated with the results from spectroscopy and imaging due to the promising developments in polarimetry achieved over the last decade. In this perspective, the advanced surveyor of transient events and nuclear astrophysics mission which includes a narrow field telescope (NFT) that comprises a wide band Laue lens (60–600 keV) associated with a high performance thick and stacked CdZnTe focal plane operating as spectrometer, imager, and scattering polarimeter has been submitted for the ESA Voyage 2050 long term scientific planning preparation. In this context, and with the aim of optimizing the focal plane configuration of an instrument such as NFT, several studies are underway. In particular, with this work we study some performance issues such as polarimeters of segmented semiconductor detectors at room temperature, such as CdZnTe and cadmium telluride (CdTe), by means of a prototype based on two planar CdTe spectroimagers operating in coincidence. The two CdTe detectors are 2-mm-thick crystals with the anode segmented in $8\times8$ pixels with 2-mm pitch. This prototype configuration allows the Compton polarimetric performance of a spectroimager to be assessed by changing the distance between the two detection layers while operating in the 100–600-keV energy range, thereby allowing the analysis of Compton polarimetry 3-D dependence. The results obtained provide relevant input to the design of large sensitive volume multilayer and 3-D sensitive focal planes.

Spectral analysis of the photoconductivity for characterization of CdTe И CdZnTe detectors

The results of the application of optical methods are considered: spectral analysis of photoconductivity in the range 400–1800 nm and field measurements of stationar photoconductivity to study the bulk and surface characteristics of CdTe and CdZnTe gamma-ray detectors. The studies of the photoresponse of the samples were carried out in different irradiation modes: modulated at a frequency of 25 Hz and a constant light flux. The measurements were carried out at room temperature on domestic and foreign materials of detector quality. Using the spectral photoconductivity method, the parameters of deep levels, which affect the detector properties, have been estimated in the studied materials. Based on the calculations of the field dependences of the photoconductivity, the volume and surface parameters of the capture and recombination of non-equilibrium carriers in the investigated detectors were determined. The results of calculating the transport characteristics of charge transfer by electrons μτe in detectors are compared with similar parameters measured using the traditional method of irradiating the detector with alpha particles. To measure the band gap in CdTe and CdZnTe at room temperature the method was modified for calculating ΔEg. The possibility of monitoring the Zn content in CdZnTe detectors using the spectral photoconductivity method is shown.