Bulk Growth of CdZnTe/CdTe Crystals

Noda, A.; Kurita, H.; Hirano, R.

doi:10.1002/9780470669464.ch2

Cited by 3 publications

(1 citation statement)

References 21 publications

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“…Produced crystals are characterized using various techniques. X-ray diffraction (XRD), infrared (IR) transmission, etch-pit density (EPD), and surface roughness (Rrms) are the primary material characterization techniques or parameters for CdZnTe material technology [6].…”

Section: Introductionmentioning

confidence: 99%

CdZnTe BULK-CRYSTAL GROWTH AND SURFACE PROCESSING TECHNOLOGY AT METU-CGL

Ergunt¹,

Kabukcuoglu²,

Balbaşı³

et al. 2020

RAP 2019 Conference Proceedings

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The study of Cd1-xZnxTe (Cadmium Zinc Telluride) bulk-crystal growth and surface processing technology at the Middle East Technical University (METU) began in 2012. The initial R&D efforts were started with the growing of CdZnTe ingots up to a size of 15 mm in diameter in a three-zone vertical Bridgman furnace located in a limited laboratory area of 15 m 2 . Following promising development in terms of single crystal yield and the crystal growth process, a new vertical gradient freeze (VGF) multi-zone furnace setup was designed and developed to accommodate the production of 60 mm diameter CdZnTe ingots. The entire furnace setup is located in a newly founded 90 m 2 laboratory named the METU Crystal Growth Laboratory (METU-CGL) in 2013. The laboratory is fully dedicated to the CdZnTe material growth and surface processing technology. Currently, METU-CGL is capable of producing 60 mm diameter CdZnTe ingots with one large grain and a few small grains. CdZnTe material is continuously grown in order to serve as either a substrate material (Cd0.96Zn0.04Te) for infrared detectors or an active material (Cd0.90Zn0.10Te) for X-ray/Gamma-ray detectors. As a typical yield, 2-3 oriented wafers per radial slice are retrieved from the grown ingots. The target wafer dimensions are 20 mm x 20 mm; however, larger or smaller crystals can be obtained based on the application of interest. The crystalline quality of the produced crystals is way below 50 arcsec of FWHM (Full width at half maximum) values from the DCRC (Double crystal rocking curves) measurements and the EPD (Etch-pit density) values are typically mid-10 4 /cm 2 . Infrared (IR) transmission of the home-grown CdZnTe crystals is exceeding 60% and stays constant within 2-20 µm wavelength interval showing that the crystals have low density of inclusions and precipitates. Not only limited to CdZnTe bulk growth technology, the METU-CGL is also capable of slicing and surface processing technologies including optimized lapping, rough mechanical polishing, and performing final chemo-mechanical polishing steps with extreme care regarding surface roughness and subsurface damage. Achievable surface roughness values of produced wafers are well below 0.5 nm (Rrms). Various state-of-theart characterization techniques including HRTEM (High-resolution transmission electron microscopy) and APT (Atom probe tomography) were conducted to study nanoscale defects in CdZnTe as a material property. This paper reviews many aspects of CdZnTe bulk-growth, surface finishing, and characterization technologies at METU-CGL as well as the laboratory infrastructure itself.

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Section: Introductionmentioning

confidence: 99%

CdZnTe BULK-CRYSTAL GROWTH AND SURFACE PROCESSING TECHNOLOGY AT METU-CGL

Ergunt¹,

Kabukcuoglu²,

Balbaşı³

et al. 2020

RAP 2019 Conference Proceedings

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Characterization of (111)B and (211)B CdZnTe Substrates for HgCdTe Growth

Haakenaasen

Lauten

Selvig

et al. 2019

Journal of Elec Materi

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We have studied state-of-the-art CdZnTe (211)B and (111)B substrates and compared them to each other and to substrates from an alternative vendor. The CdZnTe surface has been characterized both as-received and after growth preparation procedures using dark field optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, atomic force microscopy, Fourier transform infrared transmission spectroscopy, and secondary ion mass spectroscopy. From these measurements we have obtained densities of particles and morphological defects with size > 0.5 m, densities of small particles/features with size  100 nm, and substrate/film interface impurities. The state-of-the-art substrates all have remains of silica grit polishing particles around the edges. The as-received (111)B substrates had very few particles or morphological defects on the surface, but a Br:methanol surface preparation etch exposed a large number of features with sizes  100 nm. Some of these were silica grit particles, but most of them were Te precipitates. The (111)B substrate from an alternative vendor had a lot of different particles, stains, and voids. It improved significantly after a finepolishing procedure, but still had the surface with most defects after surface preparation. The state-of-the-art (211)B had the largest as-received density of small features, but after Br:methanol etching this density (of Te precipitates and silica grit particles) was the same as for the etched (111)B substrate. SIMS measurements showed that some of the polishing grit particles ended up on the top surface after surface preparation.Hydrofluoric acid can be used to etch away the silica particles.

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Carrier density and lifetime for different dopants in single-crystal and polycrystalline CdTe

et al. 2016

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CdTe defect chemistry is adjusted by annealing samples with excess Cd or Te vapor with and without extrinsic dopants. We observe that Group I (Cu and Na) elements can increase hole density above 1016 cm−3, but compromise lifetime and stability. By post-deposition incorporation of a Group V dopant (P) in a Cd-rich ambient, lifetimes of 30 ns with 1016 cm−3 hole density are achieved in single-crystal and polycrystalline CdTe without CdCl2 or Cu. Furthermore, phosphorus doping appears to be thermally stable. This combination of long lifetime, high carrier concentration, and improved stability can help overcome historic barriers for CdTe solar cell development.

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Bulk Growth of CdZnTe/CdTe Crystals

Cited by 3 publications

References 21 publications

CdZnTe BULK-CRYSTAL GROWTH AND SURFACE PROCESSING TECHNOLOGY AT METU-CGL

CdZnTe BULK-CRYSTAL GROWTH AND SURFACE PROCESSING TECHNOLOGY AT METU-CGL

Characterization of (111)B and (211)B CdZnTe Substrates for HgCdTe Growth

Carrier density and lifetime for different dopants in single-crystal and polycrystalline CdTe

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