Macro- and microsegregation of Zn in bridgman-grown CdZnTe

Autor: J. E. Harris, C. L. Jones, E. O'Keefe, I. G. Gale, P. Capper
Rok vydání: 1995
Předmět:
Zdroj: Advanced Materials for Optics and Electronics. 5:101-108
ISSN: 1099-0712
1057-9257
Popis: One of the remaining problems in the use of CdZnTe material as substrates in liquid phase epitaxy (LPE) of CdxHg1-xTe (CMT) layers is that of variation in lattice matching, i.e. Zn content, across substrates. This wil become increasingly important in the future as larger focal plane arrays of infrared detectors are required. The basic Bridgman growth process for CdTe/Cd0.96Zn0.04Te has been extended by applying the accelerated crucible rotation technique (ACRT). A marked reduction in axial Zn segregtion is seen in 50 mm diameter ACRT material, but this effect is smaller in the case of 75 mm diameter crystals. Radial variations in Zn content are small in both sizes of crystal, demonstrating the benefits obtained from ACRT stirring. Both macro- and microsegregation effects have been studied in these crystals in an attempt to understand the growth mechanism. Zinc distributions have been assessed by near-infrared transmission, X-ray lattice parameter measurements, atomic absorption spectrometry (AAS) and Auger electron spectrometry (AES). The last technique was used for the microsegregation studies, while AAS provides the absolute calibration for Zn content. Comparisons with segregation behaviour found in the literature will be given. It will be shown that the low temperature gradient and low growth rate lead to a degree of supercooling in the first-to-freeze region and this leads to significant Zn segregation in both radial and axial directions. As the crystals reach full diameter, the radial variation is decreased, presumably by the action of the ACRT, and axial segregation is also reduced.
Databáze: OpenAIRE
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