Mercury diffusion in Hg1−xCdxTe

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 betweenxCd= 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,D1andD2, from the near surface and deeply penetrating components, respectively. Our results forD1andD2are compared with other work. For bulk material annealed at 400° C under a saturated mercury pressureD1= 2.0 x 10-12cm2s-1 andD2= 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 ofD1= 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.