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19 February 2009 Effect of ampoule coating technology on defects in CdZnTe crystal
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Inclusions and micro-defects revealed by etch pits are the main defects of CdZnTe crystal, which can not be eliminated thoroughly at present. These defects will affect the photoelectric characteristic of CdZnTe and the quality of the MCT epilayer used for the infrared detectors. Many technologies are employed to suppress or eliminate the defects of CdZnTe materials, and one of them is ampoule coating technology. In the paper, ordinary carbon coating, improved carbon coating and BN (Boron Nitride) coating technology were used to study their effects on defects in CdZnTe crystal. After carbon coating technology was improved, the size of inclusion in the crystal had an obvious decrease from more than 30 μm to less than 15 μm, the density of inclusion reduced from 3~6×104cm-3 to 2×104cm-3, and etch pits density(EPD) reduced from 1×105cm-2 to less than 5×104cm-2. This meant carbon film breaking off from the ampoule was major factors to form inclusion with high density and large size, and high EPD might be relative with impurities in the material. The size of inclusions and the densities of inclusion and etch pits could be further decreased to less than 5 μm, 4×103cm-3 and 1×104cm-2 respectively after taking BN coating technology, while cell structure of etch pits found in the previous CdZnTe wafers disappeared. This result further showed that high density of inclusion and EPD originated from carbon impurities in the materials.
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Congfeng Liu, Shiwen Sun, and Hualian Xu "Effect of ampoule coating technology on defects in CdZnTe crystal", Proc. SPIE 7279, Photonics and Optoelectronics Meetings (POEM) 2008: Optoelectronic Devices and Integration, 72791I (19 February 2009);

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