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1.
Characterization of large single-crystal gamma-ray detectors of cadmium zinc telluride 总被引:2,自引:0,他引:2
A. Burger M. Groza Y. Cui D. Hillman E. Brewer A. Bilikiss G. W. Wright L. Li F. Lu R. B. James 《Journal of Electronic Materials》2003,32(7):756-760
The need for large, room-temperature gamma-ray spectrometers to be fabricated from a single crystalline section of a cadmium
zinc telluride (CZT) boule was recently met by progress in crystal growth of high-resistivity material. The characterization
of such large crystals provides us with an opportunity to better understand the detector physics and apply characterization
techniques, which were difficult to implement and analyze on smaller crystals. In this study, metal-semiconductor-metal, planar-CZT
detectors were fabricated from large (approximately 9 × 9 × 6 mm3), CZT single crystals. We have investigated the relationship between the results of the electric-field mapping via Pockels
effect, photoconductivity data, and detector performance. Changes in the surface recombination and device characteristics
showing departure from symmetry are caused and revealed by variations in the surface preparation. 相似文献
2.
Device simulations of (1) the laterally contacted-unipolar-nuclear detector (LUND), (2) the SpectrumPlus, (3) and the coplanar
grid made of Cd0.9Zn0.1Te (CZT) were performed for 137Cs irradiation by 662.15 keV gamma-rays. Realistic and controlled simulations of the gamma-ray interactions with the CZT material
were done using the MCNP4B2 Monte Carlo program, and the detector responses were simulated using the Sandia three-dimensional
multi-electrode simulation program (SandTMSP). The simulations were done for the best and the worst expected carrier mobilities
and lifetimes of currently commercially available CZT materials for radiation detector applications. For the simulated unipolar
devices, the active device volumes were relatively large and the energy resolutions were fairly good, but these performance
characteristics were found to be very sensitive to the materials properties. The internal electric fields, the weighting potentials,
and the charge induced efficiency maps were calculated to give insights into the operation of these devices. 相似文献
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R. B. James B. Brunett J. Heffelfinger J. Van Scyoc J. Lund F. P. Doty C. L. Lingren R. Olsen E. Cross H. Hermon H. Yoon N. Hilton M. Schieber E. Y. Lee J. Toney T. E. Schlesinger M. Goorsky W. Yao H. Chen A. Burger 《Journal of Electronic Materials》1998,27(6):788-799
The material showing the greatest promise today for production of large-volume gamma-ray spectrometers operable at room temperature
is cadmium zinc telluride (CZT). Unfortunately, because of deficiencies in the quality of the present material, high-resolution
CZT spectrometers have thus far been limited to relatively small dimensions, which makes them inefficient at detecting high
photon energies and ineffective for weak radiation signals except in near proximity. To exploit CZT fully, it will be necessary
to make substantial improvements in the material quality. Improving the material involves advances in the crystallinity, purity,
carrier lifetimes, and control of the electrical compensation mechanism. A more detailed understanding of the underlying material
problems limiting the performance of CZT gamma-ray detectors is required; otherwise, problems with supply, delivery times,
and unit cost of large-volume (>5 cm3 active volume) CZT spectrometers are expected to continue. A variety of analytical and numerical techniques have been employed
to quantify crystallinity, strain, impurities, compositional and stoichiometric variations, bulk and surface defect states,
carrier mobilities and lifetimes, electric field distributions, and surface passivation. Data from these measurements were
correlated with spatial maps of the gamma-ray and alpha particle spectroscopic response, and feedback on the effectiveness
of crystal growth and detector fabrication procedures has been generated. The results of several of these analytical techniques
will be presented in this paper. 相似文献
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T. S. Lee K. K. Choi Y. T. Jeoung H. K. Kim J. M. Kim Y. H. Kim J. M. Chang W. S. Song S. U. Kim M. J. Park S. D. Lee 《Journal of Electronic Materials》1997,26(6):552-555
In this paper, we report the results of capacitance-voltage measurements conducted on several metal-insulator semiconductor (MIS) capacitors in which HgCdTe surfaces are treated with various surface etching and oxidation processes. CdZnTe passivation layers were deposited on HgCdTe surfaces by thermal evaporation after the surfaces were etched with 0.5?2.0% bromine in methanol solution, or thin oxide layers (tox ~ few ten Å) were grown on the surfaces, in order to investigate effects of the surface treatments on the electrical properties of the surfaces, as determined from capacitance-voltage (C-V) measurements at 80K and 1 MHz. A negative flat band voltage has been observed for MIS capacitors fabricated after etching of HgCdTe surfaces with bromine in methanol solutions, which is reported to make the surface Te-rich. It is inferred that residual Te on the surface is a positive charge, Te4+. C-V characteristics for MIS capacitors fabricated on oxide surfaces grown by air-exposure and electrolytic process have shown large hysteresis effects, from which it is inferred that imperfect and electrically active oxide compounds and HgTe particles near the surface become slow interface states. 相似文献
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G. L. Martinez M. R. Curiel B. J. Skromme R. J. Molnar 《Journal of Electronic Materials》2000,29(3):325-331
The surface recombination velocity in n-type heteroepitaxial GaN(0001) is shown to decrease dramatically when the surface
is chemically treated with aqueous and alcoholic solutions of inorganic sulfides, such as ammonium or sodium sulfide (NH4)2Sx and Na2S). The room-temperature excitonic photoluminescence (PL) intensity increases by a factor of four to six after treatment,
and improvements persist for at least seven months in room air. Various other chemicals commonly used in device processing
are investigated and shown to change the PL intensity by factors ranging from 0.7 to 2.5, buffered oxide etching being the
most beneficial. Schottky barrier diodes using gold as the contact metal are fabricated using a sulfide treatment prior to
evaporation. The barrier height from capacitance-voltage measurements is as high as 1.63 ± 0.07 V, the highest value ever
achieved on n-GaN. This result is evidence that the effect of surface states on the Fermi level has been substantially reduced
by the treatment. 相似文献
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SHORT COMMUNICATION: Surface passivation by rehydrogenation of silicon‐nitride‐coated silicon wafers
Michelle McCann Klaus Weber Andrew Blakers 《Progress in Photovoltaics: Research and Applications》2005,13(3):195-200
A silicon wafer with a silicon nitride layer deposited by low pressure chemical vapour deposition may be subjected to high‐temperature treatments without adversely affecting the electronic properties of the silicon on the condition that a thin oxide is present under the nitride. After high‐temperature treatments there is an apparent degradation in effective lifetime, probably due to a loss of hydrogen from the silicon/oxide interface. Effective lifetimes can be completely recovered by thermal treatment in a hydrogen‐containing ambient. This work has useful applications for solar cells as many of the properties of these nitrides can be used to advantage. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
11.
Hichem M'saad Jurgen Michel J. J. Lappe L. C. Kimerling 《Journal of Electronic Materials》1994,23(5):487-491
We report the electronic passivation of a silicon surface by iodine termination. The resulting surface recombination velocity
on Si(100) is less than 1 cm/s which is better than that obtained in concentrated hydrofluoric acid (HF). We have produced
a surface recombination velocity of 20 cm/s using bromine. We present a simple model for these phenomena of a surface coverage
of Si-X where X is a monovalently bonded halogen atom. The effectiveness of the passivation by halogens is shown to be limited
by the oxidation of halogens by dissolved oxygen in solution. We demonstrate the use of halogen:methanol solutions as an alternative
to HF for the control of silicon surface chemistry. 相似文献
12.
R. Rafiei M. I. Reinhar A. Sarbutt S. Ux D. Boardman G. C. Watt E. Belas K. Kim A. E. Bolotnikov R. B. James 《半导体学报》2013,34(7):073001-7
Charge transport characteristics of Cd0.95Mn0.05Te:In radiation detectors have been evaluated by combining time resolved current transient measurements with time of flight charge transient measurements.The shapes of the measured current pulses have been interpreted with respect to a concentration of net positive space-charge, which has resulted in an electric field gradient across the detector bulk.From the recorded current pulses the charge collection efficiency of the detector was found to approach 100%.From the evolution of the charge collection efficiency with applied bias,the electron mobility-lifetime product ofμnτn =(8.5±0.4)×10-4 cm2/V has been estimated.The electron transit time was determined using both transient current technique and time of flight measurements in the bias range of 100-1900 V.From the dependence of drift velocity on applied electric field the electron mobility was found to beμn =(718±55) cm2/(V·s) at room temperature. 相似文献
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赝二元体系碲镉汞(Mercury Cadmium Telluride, HgxCd1-xTe)材料具有优异的光电特性,是制备高灵敏度红外探测器的最重要材料之一。为了获得性能优异的HgxCd1-xTe探测器及其组件,目前已经发展了各种HgxCd1-xTe材料制备技术和器件制作工艺。但在各种材料制备及器件应用过程中,HgxCd1-xTe表面均会受到环境和不良表面效应的影响,所以需要采用先进的钝化工艺对其表面电荷态进行处理,改善材料表面的电学物理特性,从而实现器件探测性能的提升。因此,HgxCd1-xTe薄膜表面钝化工艺对HgxCd1-xTe红外探测器的性能提升至关重要。总结和分析了近年来碲镉汞薄膜表面钝化层的生长方法。按照本源钝化和非本源钝化进行了分类总结和综述,分析了不同钝化方法的优缺点,并对未来碲镉汞薄膜钝化工艺进行了展望。 相似文献
15.
Muren Chu Sevag Terterian David Ting C. C. Wang J. D. Benson J. H. Dinan R. B. James Arnold Burger 《Journal of Electronic Materials》2003,32(7):778-782
Room-temperature radiation detectors have been fabricated on high-resistivity, indium-doped Cd0.90Zn0.10Te crystals grown under different amounts of excess Te. The effects of the excess Te on the properties of the detectors are
explained by a simple model using only three parameters: the density of Cd vacancies, the density of Te antisites (Te at Cd
sites), and the deep level of doubly ionized Te antisites. The best detectors, which can resolve the low-energy Np-L and Te-K
peaks as well as Cd and Te escape peaks of 241Am, are produced from crystals grown with 1.5% excess Te. The detectors fabricated from crystals grown without excess Te are
unable to resolve any characteristic-radiation peaks of 241Am and 57Co. This result is explained by a model of networked p-type domains in an n-type matrix or vice versa, which is caused by
the lack of sufficient deep-level Te antisites. Such conduction-type inhomogeneity causes massive electron and hole trapping.
As for the detectors fabricated from Cd0.90Zn0.10Te crystals grown with 2% and 3% excess Te, they are able to resolve the 241Am 59.5-keV, 57Co 122-keV, and 57Co 136-keV radiation peaks. However, the full-width at half-maximum (FWHM) values of these peaks are broadened, especially
the high-energy 57Co peaks. These phenomena are attributed to the hole and, possibly, electron trapping by Cd vacancies and Te antisites, respectively.
The result of the analysis indicates that sufficient Te antisites and a low density of carrier traps in Cd0.90Zn0.10Te are essential for producing high-quality radiation detectors. In the analysis, it was discovered that most of the excess
Te, on the order of 1–2 × 1020 cm−3, remain electrically inactive. A possible explanation for this phenomenon is that the excess Te atoms form neutral Te-antisite
and Cd-vacancy complexes, such as TeCd·(VCd)2, during the post-growth cooling process. 相似文献
16.
Tsu‐Tsung Andrew Li Andres Cuevas 《Progress in Photovoltaics: Research and Applications》2011,19(3):320-325
Aluminum oxide films can provide excellent surface passivation on both p‐type and n‐type surfaces of silicon wafers and solar cells. Even though radio frequency magnetron sputtering is capable of depositing aluminum oxide with concentrations of negative charges comparable to some of the other deposition methods, the surface passivation has not been as good. In this paper, we compare the composition and bonding of aluminum oxide deposited by thermal atomic layer deposition and sputtering, and find that the interfacial silicon oxide layer and hydrogen concentration can explain the differences in the surface passivation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
The thermal ionization energies of traps and their types, whether electron or hole traps, were measured in commercial CdZnTe
crystals for radiation detectors. The measurements were done between 20 and 400K using thermoelectric emission spectroscopy
(TEES) and thermally stimulated conductivity (TSC). For reliable results, indium ohmic contacts had to be used instead of
gold Schottky contacts. For filling of the traps, photoexcitation was done at zero bias, at 20K, and at wavelengths which
gave the maximum bulk photoexcitation. In agreement with theory, the TSC current was found to be on the order of
times or even larger than the TEES current, where V is the applied bias in TSC and ΔT is the applied temperature difference
in TEES. Large concentrations of hole traps at 0.1 and 0.6 eV were observed and a smaller concentration of electron traps
at 0.4 eV was seen. The deep traps cause compensation in the material, which is desirable, but they also cause carrier trapping
that degrades the spectral response of radiation detectors made from the material. 相似文献
18.
Solution-processed oxide semiconductors have been considered as a potential alternative to vacuum-based ones in printable electronics. However, despite spin-coated InZnO (IZO) thin-film transistors (TFTs) have shown a relatively high mobility, the lack of carrier suppressor and the high sensitivity to oxygen and water molecules in ambient air make them potentially suffer issues of poor stability. In this work, Al is used as the third cation doping element to study the effects on the electrical, optoelectronic, and physical properties of IZO TFTs. A hydrophobic self-assembled monolayer called octadecyltrimethoxysilane is introduced as the surface passivation layer, aiming to reduce the effects from air and understand the importance of top surface conditions in solution-processed, ultra-thin oxide TFTs. Owing to the reduced trap states within the film and at the top surface enabled by the doping and passivation, the optimized TFTs show an increased current on/off ratio, a reduced drain current hysteresis, and a significantly enhanced bias stress stability, compared with the untreated ones. By combining with high-capacitance AlOx, TFTs with a low operating voltage of 1.5 V, a current on/off ratio of > 104 and a mobility of 4.6 cm2/(V·s) are demonstrated, suggesting the promising features for future low-cost, low-power electronics. 相似文献
19.
J. Schmidt A. Merkle R. Brendel B. Hoex M. C. M. van de Sanden W. M. M. Kessels 《Progress in Photovoltaics: Research and Applications》2008,16(6):461-466
Atomic‐layer‐deposited aluminium oxide (Al2O3) is applied as rear‐surface‐passivating dielectric layer to passivated emitter and rear cell (PERC)‐type crystalline silicon (c‐Si) solar cells. The excellent passivation of low‐resistivity p‐type silicon by the negative‐charge‐dielectric Al2O3 is confirmed on the device level by an independently confirmed energy conversion efficiency of 20·6%. The best results are obtained for a stack consisting of a 30 nm Al2O3 film covered by a 200 nm plasma‐enhanced‐chemical‐vapour‐deposited silicon oxide (SiOx) layer, resulting in a rear surface recombination velocity (SRV) of 70 cm/s. Comparable results are obtained for a 130 nm single‐layer of Al2O3, resulting in a rear SRV of 90 cm/s. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
20.
Dong-Su Kim Chih-Ping Chao Kian Beyzavi Paul E. Burrows Stephen R. Forrest 《Journal of Electronic Materials》1996,25(3):537-540
We report for the first time, a surface passivation technique for InP/In0.53Ga0.47As heterojunction bipolar transistors that is suitable for optoelectronic integrated circuits. The combination of buffered
hydrofluoric acid with high temperature annealing of the surface causes significant increase of the gain at low input currents.
Using this technique, transistors were integrated with photodetectors and other optoelectronic devices and had current gains
as high as 400 even at nanoampere base currents. 相似文献