Measurement of the drift mobilities and the mobility-lifetime products of charge carriers in a CdZnTe crystal by using a transient pulse technique

Cho, H Y; Lee, J H; Kwon, Young–Kyu; Moon, Jae-Duk; Lee, C S

doi:10.1088/1748-0221/6/01/c01025

Cited by 28 publications

(14 citation statements)

References 14 publications

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“…Biasing the sample mounted on a heat sink in quasi continuous mode up to 165 V resulted in a perfectly linear I−V curve (Figure 5b), with no nonlinearities at higher biases indicative for carrier trapping. With the same pulsed quasi-continuous mode biasing the field dependence of the photoconductivity was measured, which can be fitted by the Hecht formula 72 to provide a mobility lifetime product of μτ = 8.8 × 10 −5 cm 2 /V (Figure 5c). To obtain the carrier lifetime, transient photoconductivity was measured from the pellets, and from the photoconductivity decays a lifetime of 69 μs is deduced (Figure 5d).…”

Section: Resultsmentioning

confidence: 99%

Quasi-epitaxial Metal-Halide Perovskite Ligand Shells on PbS Nanocrystals

et al. 2017

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Epitaxial growth techniques enable nearly defect free heterostructures with coherent interfaces, which are of utmost importance for high performance electronic devices. While high-vacuum technology-based growth techniques are state-of-the art, here we pursue a purely solution processed approach to obtain nanocrystals with eptaxially coherent and quasi-lattice matched inorganic ligand shells. Octahedral metal-halide clusters, respectively 0-dimensional perovskites, were employed as ligands to match the coordination geometry of the PbS cubic rock-salt lattice. Different clusters (CHNH)[MHal] (M = Pb(II), Bi(III), Mn(II), In(III), Hal = Cl, I) were attached to the nanocrystal surfaces via a scalable phase transfer procedure. The ligand attachment and coherence of the formed PbS/ligand core/shell interface was confirmed by combining the results from transmission electron microscopy, small-angle X-ray scattering, nuclear magnetic resonance spectroscopy and powder X-ray diffraction. The lattice mismatch between ligand shell and nanocrystal core plays a key role in performance. In photoconducting devices the best performance (detectivity of 2 × 10 cm Hz /W with> 110 kHz bandwidth) was obtained with (CHNH)BiI ligands, providing the smallest relative lattice mismatch of ca. -1%. PbS nanocrystals with such ligands exhibited in millimeter sized bulk samples in the form of pressed pellets a relatively high carrier mobility for nanocrystal solids of ∼1.3 cm/(V s), a carrier lifetime of ∼70 μs, and a low residual carrier concentration of 2.6 × 10 cm. Thus, by selection of ligands with appropriate geometry and bond lengths optimized quasi-epitaxial ligand shells were formed on nanocrystals, which are beneficial for applications in optoelectronics.

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Section: Resultsmentioning

confidence: 99%

Quasi-epitaxial Metal-Halide Perovskite Ligand Shells on PbS Nanocrystals

et al. 2017

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“…2). For the simplest case, that is a single kind of charge carriers originating from the absorption of photons by the device surface, CCE can be expressed with the Hecht equation 46 :…”

Section: Detection Efficiency and Charge Transport Properties Of Mapbi3 Sc The Highest De-values Are Expected Inmentioning

confidence: 99%

Stable near-to-ideal performance of a solution-grown single-crystal perovskite X-ray detector

Kovalenko

Sakhatskyi

Türedi

et al. 2021

Preprint

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The ideal photodetector is the one able to detect every single incoming photon. In particular, in X-ray medical imaging, the radiation dose for patients can then approach its fundamentally lowest limit set by the Poisson photon statistics. Such near-to-ideal X-ray detection characteristics have been demonstrated with only a few semiconductor materials such as Si1 and CdTe2; however, their industrial deployment in medical diagnostics is still impeded by elaborate and costly fabrication processes. Hybrid metal halide perovskites – newcomer semiconductors -– make for a viable alternative3,4,5 owing to their scalable, inexpensive, robust, and versatile solution growth and recent demonstrations of single gamma-photon counting under high applied bias voltages6,7. The major hurdle with perovskites as mixed electronic-ionic conductors, however, arises from the rapid material's degradation under high electric field8,9,10,11, thus far used in perovskite X-ray detectors12,13. Here we show that both near-to-ideal and long-term stable performance of perovskite X-ray detectors can be attained in the photovoltaic mode of operation at zero-voltage bias, employing thick and uniform methylammonium lead iodide (MAPbI3) single crystal (SC) films (up to 300 µm), solution-grown directly on hole-transporting electrodes. The operational device stability is equivalent to the intrinsic chemical shelf lifetime of MAPbI3, being at least one year in the studied case. Detection efficiency of 88% and noise equivalent dose of 90 pGyair (lower than the dose of a single incident photon) are obtained with 18 keV X-rays, allowing for single-photon counting, as well as low-dose and energy-resolved X-ray imaging. These findings benchmark hybrid perovskites as practically suited materials for developing low-cost commercial detector arrays for X-ray imaging technologies.

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“…1,3 The charge trapping affects the energy resolution through the carrier lifetime more than through the mobility. 7 It is shown that the effective carrier lifetime determined from the initial portion of the transients combines both recombination and trapping in a manner similar to the conventional 2-step approach, which determines carrier lifetime by measurement of the mobilitylifetime product (ls) and the carrier drift mobility using a TOF method. 6,8 The RF-based measurements of this parameter allow rapid, non-contact characterization of the crystal properties.…”

Section: Discussionmentioning

confidence: 99%

“…7 This becomes an essential motivation for introduction of the non-contact measurements of the effective carrier lifetime that combines both recombination and trapping of carriers in a manner similar to the conventional 2-step approach. 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.…”

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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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Measurement of the drift mobilities and the mobility-lifetime products of charge carriers in a CdZnTe crystal by using a transient pulse technique

Cited by 28 publications

References 14 publications

Quasi-epitaxial Metal-Halide Perovskite Ligand Shells on PbS Nanocrystals

Quasi-epitaxial Metal-Halide Perovskite Ligand Shells on PbS Nanocrystals

Stable near-to-ideal performance of a solution-grown single-crystal perovskite X-ray detector

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

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