Extended Defects in CdZnTe Radiation Detectors

Bolotnikov, A. E.; Babalola, Stephen; Camarda, G. S.; Chen, H.; Awadalla, Salah; Cui, Yonggang; Egarievwe, Stephen U.; Fochuk, P.; Hawrami, R.; Hossain, Anwar; James, J.R.; Nakonechnyj, I. J.; Mackenzie, J.; Yang, Ge; Xu, Chao; James, R. B.

doi:10.1109/tns.2009.2019960

Cited by 65 publications

(36 citation statements)

References 16 publications

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“…1,2 However, their ultimate energy resolution has been largely limited by defects formed during crystal growth, including point defects, dislocations, and grain boundaries, because these defects often behave as charge trapping centers for electrons or holes and either induce recombination or delay carrier collection. [3][4][5][6][7] Among various defects, dislocations are of particular interest in CdTe, as they have been experimentally observed to cause defect states within the band gap and show a strong correlation between their spatial distributions and substantial charge trapping in devices excited by X-rays. [7][8][9][10] However, as dislocations often are found decorated with impurities or Te-rich secondary phases (Te precipitates or inclusions) 5,7 , it is difficult to determine experimentally whether the charge carrier trapping is primarily due to the dislocations themselves or their decorating defects.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5][6][7] Among various defects, dislocations are of particular interest in CdTe, as they have been experimentally observed to cause defect states within the band gap and show a strong correlation between their spatial distributions and substantial charge trapping in devices excited by X-rays. [7][8][9][10] However, as dislocations often are found decorated with impurities or Te-rich secondary phases (Te precipitates or inclusions) 5,7 , it is difficult to determine experimentally whether the charge carrier trapping is primarily due to the dislocations themselves or their decorating defects. Thus, theoretical calculations are necessary to elucidate the specific role of dislocations on carrier trapping in Cd(Zn)Te, separated from the decorating defects.…”

Section: Introductionmentioning

confidence: 99%

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First-principles study of atomic and electronic structures of60∘perfect and30∘/90∘partial glide dislocations in CdTe

2016

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The atomic and electronic structures of 60• glide perfect and 30• /90• glide partial dislocations in CdTe are studied using combined semi-empirical and density functional theory calculations. The calculations predict that the dislocation cores tend to undergo significant reconstructions along the dislocation lines from the singly-periodic (SP) structures, yielding either doubly-periodic (DP) ordering by forming a dimer or quadruplyperiodic (QP) ordering by alternating a dimer and a missing dimer. Charge modulation along the dislocation line, accompanied by the QP reconstruction for the Cd-/Te-core 60• perfect and 30• partials or the DP reconstruction for the Cd-core 90• partial, results in semiconducting character, as opposed to the metallic character of the SP dislocation cores. Dislocation-induced defect states for the 60• Cd-/Te-core are located relatively close to the band edges, whereas the defect states lie in the middle of the band gap for the 30• Cd-/Te-core partial dislocations. In addition to the intra-core charge modulation within each QP core, the possibility of inter-core charge transfer between two different dislocation cores when they are paired together in the same system is discussed. The analysis of the electronic structures reveals the potential role of the dislocations on charge transport in CdTe, particularly in terms of charge trapping and recombination.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First-principles study of atomic and electronic structures of60∘perfect and30∘/90∘partial glide dislocations in CdTe

2016

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“…Earlier, our group described how to read data and find inclusions using this IDL program [9]. Extended defects inside CZT crystals, such as dislocations and low-angle sub-grain boundaries, are apparent with the IR transmission microscopy system only when Te inclusions decorate them; otherwise, they are not readily visible with the IR images [11]. Hence, we used the set-up for White Beam X-ray Diffraction Topography (WBXDT) at beamline X19C ( Fig.…”

Section: (A)mentioning

confidence: 99%

Extended defects in As-grown CdZnTe

Bolotnikov

Hossain

et al. 2010

SPIE Proceedings

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We characterized samples cut from different locations in as-grown CdZnTe (CZT) ingots, using Automated Infrared (IR) Transmission Microscopy and White Beam X-ray Diffraction Topography (WBXDT), to locate and identify the extended defects in them. Our goal was to define the distribution of these defects throughout the entire ingot and their effects on detectors' performance as revealed by the pulse-height spectrum. We found the highest-and the lowest-concentration of Te inclusions, respectively, in the head and middle part of the ingot, which could serve as guidance in selecting samples.Crystals with high concentration of Te inclusions showed high leakage current and poor performance, because the accumulated charge loss around trapping centers associated with Te inclusions distorts the internal electric field, affects the carrier transport properties inside the crystal, and finally degrades the detector's performance. In addition, other extended defects revealed by the WBXDT measurements severely reduced the detector's performance, since they trap large numbers of electrons, leading to a low signal for the pulse-height spectrum, or none whatsoever. Finally, we fully correlated the detector's performance with our information on the extended defects gained from both the IR-and the WBXDT-measurements.

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“…12 Figure 5a is the IR transmission image of a CdTe film ($100 lm) after the Ge substrate had been removed, in comparison with its surface reflection image (Fig. 5b).…”

Section: Reduction In Number Of Te Inclusionsmentioning

confidence: 99%

Growth of Thick Epitaxial CdTe Films by Close Space Sublimation

Jiang

Brinkman

Cantwell

et al. 2009

Journal of Elec Materi

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This paper reports on a detailed study of the development of the close space sublimation method, which has been widely used in the preparation of polycrystalline CdTe/CdS solar cells, as an epitaxial method for the growth of thick CdTe single crystal films over 200 lm on GaAs and Ge substrates for highenergy radiation detectors. The resulting microscopic growth phenomena in the process are also discussed in this paper. High-quality single crystalline CdTe thick films were prepared with x-ray rocking curves full width at half maximum (FWHM) values, which were $100 arcsec on Ge substrates and 300 arcsec on GaAs substrates. The quality of thick films on Ge(100) showed a substantial improvement with nucleation in a Te-rich growth environment. No Te inclusions in the CdTe films grown on GaAs(211)B and Ge(100) were observed with IR transmission imaging. Photoluminescence of CdTe/Ge shows a large reduction in the 1.44 eV defect energy bands compared with films grown on GaAs substrates. The film resistivity is on the order of 10 10 X cm, and the film displayed some sensitivity to alpha particles.

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Extended Defects in CdZnTe Radiation Detectors

Cited by 65 publications

References 16 publications

First-principles study of atomic and electronic structures of60∘perfect and30∘/90∘partial glide dislocations in CdTe

First-principles study of atomic and electronic structures of60∘perfect and30∘/90∘partial glide dislocations in CdTe

Extended defects in As-grown CdZnTe

Growth of Thick Epitaxial CdTe Films by Close Space Sublimation

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