Mercury diffusion in Hg1?xCdxTe |
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Authors: | Neil Archer Helen Palfrey |
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Affiliation: | (1) Engineering Materials, University of Southampton, S09 5NH Southampton, UK;(2) Aeronautics and Astronautics Department, University of Southampton, S09 5NH Southampton, UK |
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Abstract: | A radiotracer technique has been used to measure both mercury self-diffusion and surface concentration values in bulk and
liquid phase epitaxy, LPE, grown Hg1−xCdxTe. A high resolution sectioning technique has allowed profiling of thin epitaxial layers in submicron steps. Hg1-xCdxTe samples with composition values betweenx
Cd= 0.16 and 0.23 were isothermally annealed in carefully controlled and monitored diffusion con-ditions. Mercury reservoirs
containing Hg203 were used to provide vapour diffusion sources during closed tube isothermal anneals in the temperature range 300° C to 400°
C. Evidence has been found which may indicate the presence of two components in the radio-tracer profiles for both bulk and
epitaxially grown material. In some cases it was possible to estimate two diffusion coefficients,D
1andD
2, from the near surface and deeply penetrating components, respectively. Our results forD
1andD
2are compared with other work. For bulk material annealed at 400° C under a saturated mercury pressureD
1= 2.0 x 10-12cm2s-1 andD
2= 1.1 x 10-11cm2s−1. Diffusion coefficients at 310° C under saturated mercury pressure, have been measured in bulk and epitaxial material. Close
agreement was found between these results with an average value ofD
1= 1.4 x 10−13cm2s−1. We believe this to be the first time radiotracer results for epitaxial material have been presented. We have collated diffusion
data, as a function of reciprocal temperature, from several workers and suggest there is evidence for a change in the activation
energy for mercury diffusion around 350° C. This may be due to a change in the dominant diffusion mechanism. |
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Keywords: | HgCdTe self diffusion Hg diffusion |
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