Comparison of the diffusion of Hg into CdTe and Hg0.8Cd0.2Te

In this paper, results published recently on Hg diffusion in the important infrared detector material, Hg_0.8Cd_0.2Te, and its common substrate material, CdTe, are compared and discussed. As is customary with diffusion studies in II-VI semiconductors, two component profiles were obtained in the majority of cases, each profile giving two values of the diffusivity. The values of D for the mercury diffusion in CdTe were much less than corresponding values in Hg_0.8Cd_0.2Te diffusion proceeds by volume diffusion followed by short circuit diffusion, whereas in CdTe diffusion is rate limiting volume diffusion involving a slow stream and a fast stream. From pressure dependency measurements, it is proposed that the slow component occurs by an interstitial mechanism at low P_Hg and a vacancy mechanism at high P_Hg, whereas in Hg_0.8Cd_0.2Te the reverse occurs for the fast diffusion component. In CdTe, the slow component increases systematically with etch pit density, whereas in Hg_0.8Cd_0.2Te, the diffusivity is independent of the quality of the material. From the comparisons, it is seen that there are some common features in the diffusion of Hg in the two materials but there are also some clear and distinct differences.