Time of flight experimental studies of CdZnTe radiation detectors

Erickson, Jay C.; Yao, H. Walter; James, R. B.; Hermon, H.; Greaves, Mikal

doi:10.1007/s11664-000-0208-z

Cited by 53 publications

(23 citation statements)

References 2 publications

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“…The origin of the high plateau is that the mobility is high enough so that carriers escape the dense track before any significant nonlinear quenching can occur. 54 Semiconductor detectors such as HPGe (μ e = 36,000, μ h = 42,000 cm 2 /Vs), 16 CZT (CdZnTe, μ e ≈ 1120, μ h ≈ 45 cm 2 /Vs), 41 and CdTe (μ e ≈ 945, μ h ≈ 45 cm 2 /Vs) 41 are on the high plateau. Notice that the dashed curve taking μ e fixed at 8 cm 2 /Vs does not approach 1 at high μ h .…”

Section: Figmentioning

confidence: 99%

“…For the charged iodine vacancies, we choose 5 different supercells with different sizes (containing 48, 96, 144, 288, 432 atoms respectively) and relax the structures for both F -and F + center using GGA-PBE. We calculate the monopole-monopole interaction terms for each of them explicitly using the calculated static dielectric constant tensor [41] and extrapolate the corrected data assuming an L -3 dependence. Here L is defined as the cubic root of the supercell volume.…”

Section: Finite Supercell Size Correctionsmentioning

confidence: 99%

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Toward a user's toolkit for modeling scintillator non-proportionality and light yield

Williams

2014

SPIE Proceedings

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Section: Figmentioning

confidence: 99%

Section: Finite Supercell Size Correctionsmentioning

confidence: 99%

Toward a user's toolkit for modeling scintillator non-proportionality and light yield

Williams

2014

SPIE Proceedings

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“…Hole trapping is significant within CZT detectors since the hole mobility in CZT is about 20 times lower than electron mobility (Erickson et al 2000). Slowly-moving and trapped holes induce a signal component on anodes that is opposite in polarity to electrons, resulting in anode signal deficit.…”

Section: Discussionmentioning

confidence: 99%

Study of a high-resolution, 3D positioning cadmium zinc telluride detector for PET

Matteson

Skelton

et al. 2011

Phys. Med. Biol.

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This paper investigates the performance of 1 mm resolution Cadmium Zinc Telluride (CZT) detectors for positron emission tomography (PET) capable of positioning the 3-D coordinates of individual 511 keV photon interactions. The detectors comprise 40 mm × 40 mm × 5 mm monolithic CZT crystals that employ a novel cross-strip readout with interspersed steering electrodes to obtain high spatial and energy resolution. The study found a single anode FWHM energy resolution of 3.06±0.39% at 511 keV throughout most the detector volume. Improved resolution is expected with properly shielded front-end electronics. Measurements made using a collimated beam established the efficacy of the steering electrodes in facilitating enhanced charge collection across anodes, as well as a spatial resolution of 0.44±0.07 mm in the direction orthogonal to the electrode planes. Finally, measurements based on coincidence electronic collimation yielded a point spread function with 0.78±0.10 mm FWHM, demonstrating 1 mm spatial resolution capability transverse to the anodes – as expected from the 1 mm anode pitch. These findings indicate that the CZT-based detector concept has excellent performance and shows great promise for a high-resolution PET system.

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“…Conventionally, these parameters are determined by measurement of the mobilitylifetime product (ls) and calculating the carrier drift mobility from the carrier transit time measured using a TOF method. 6,8 The carrier mobility can also be calculated using the rise time of the pulse instead of the transit time. 6 Unlike the ls and TOF measurements that require using high external bias voltage to collect charge at the electrode, the RF-based method discussed in this paper does not utilize any external bias.…”

Section: Effective Carrier Lifetime In the Detector Materialsmentioning

confidence: 99%

“…The conventional 2step approach determines carrier lifetime by measurement of the mobility-lifetime product (ls) and calculating the electron drift mobility from the carrier transit time measured using a time-of-flight (TOF) method. 6,8 …”

mentioning

confidence: 99%

Effect of charge trapping on effective carrier lifetime in compound semiconductors: High resistivity CdZnTe

Kamieniecki¹

2014

Journal of Applied Physics

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The dominant problem limiting the energy resolution of compound semiconductor based radiation detectors is the trapping of charge carriers. The charge trapping affects energy resolution through the carrier lifetime more than through the mobility. Conventionally, the effective carrier lifetime is determined using a 2-step process based on measurement of the mobility-lifetime product (μτ) and determining drift mobility using time-of-flight measurements. This approach requires fabrication of contacts on the sample. A new RF-based pulse rise-time method, which replaces this 2-step process with a single non-contact direct measurement, is discussed. The application of the RF method is illustrated with high-resistivity detector-grade CdZnTe crystals. The carrier lifetime in the measured CdZnTe, depending on the quality of the crystals, was between about 5 μs and 8 μs. These values are in good agreement with the results obtained using conventional 2-step approach. While the effective carrier lifetime determined from the initial portion of the photoresponse transient combines both recombination and trapping in a manner similar to the conventional 2-step approach, both the conventional and the non-contact RF methods offer only indirect evaluation of the effect of charge trapping in the semiconductors used in radiation detectors. Since degradation of detector resolution is associated not with trapping but essentially with detrapping of carriers, and, in particular, detrapping of holes in n-type semiconductors, it is concluded that evaluation of recombination and detrapping during photoresponse decay is better suited for evaluation of compound semiconductors used in radiation detectors. Furthermore, based on previously reported data, it is concluded that photoresponse decay in high resistivity CdZnTe at room temperature is dominated by detrapping of carriers from the states associated with one type of point defect and by recombination of carriers at one type of extended defects. The recombination at the extended defects produces long, logarithmic decay limiting substantially performance of CdZnTe detectors. This decay is associated with the “electrostatic trapping” of excess holes by the Schottky-type depletion space-charge regions formed around the defects.

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Time of flight experimental studies of CdZnTe radiation detectors

Cited by 53 publications

References 2 publications

Toward a user's toolkit for modeling scintillator non-proportionality and light yield

Toward a user's toolkit for modeling scintillator non-proportionality and light yield

Study of a high-resolution, 3D positioning cadmium zinc telluride detector for PET

Effect of charge trapping on effective carrier lifetime in compound semiconductors: High resistivity CdZnTe

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