The incorporation and diffusivity of As in Hg_0.8Cd_0.2Te

摘要

The dependence to be expected by the experimentally observed diffusivity of As in Hg_0.8Cd_0.2Te, D(As), on the Hg pressure, P_Hg, and on the As concentration has been calculated for various modes of As incorporation described in the literature and for interstitial and vacancy diffusion mechanisms. Comparison with experimental data which shows D(As) to be independent of As concentration (at least up to 5 x 10~18 cm~-3), to vary as 1 /P_Hg at moderate pressures and as 1/P_Hg~3, at high pressures, confirms that these features can only be accounted for if As substitutes on the cation sub--lattice as As_Hg and on the anion sub-lattice as As_Te. Diffusion occurs on the cation sub-lattice due to the mobile As_Hg diffusing by a vacancy mechanism. Significant concentrations of As dimer or tetramer complexes give rise to D(As) depending on the As concentration as well as incorrect variations with P_Hg. A further important result is that Hg_0.8Cd_0.2Te is electrically intrinsic for these As concentrations down to at least 250 ℃.