Diffusion of Gold and Native Defects in Mercury Cadmium Telluride

摘要

The diffusion of defects is of great importance in nanoscale device fabrication, making it essential to understand theoretically the microscopic mechanisms governing how native and dopant defects diffuse. To gain this insight, we have performed, for the first time, ab initio density functional calculations to determine the diffusion barriers for multiple pathways of Au impurities and native species in mercury cadmium telluride (MCT). We consider interstitial and vacancy-mediated diffusion mechanisms and calculate the corresponding activation energies using ab initio pseudopotential total energy calculations. Depending on the stoichiometry, the activation energies for Hg self-diffusion are calculated to range from 1.35 eV to 1.60 eV (interstitial mechanism) and from 1.60 eV to 1.85 eV (vacancy mechanism). These theoretical values suggest that Hg self-diffusion is predominantly interstitial mediated, and are in good agreement with existing experimental estimates, which suggest possible activation energies ranging from 1.05 eV to 1.75 eV. For Te self-diffusion via the interstitial mechanism, the calculated activation energy ranging from 2.35 eV to 2.60 eV is also in good agreement with the experimental estimates near 2.30 eV. For Au impurities, whether they are incorporated into the interstitial or Hg site, we find the interstitial mediated mechanism to be the dominant one. Our calculated barrier of 0.35 eV for Au interstitials is also in good agreement with the experimental estimate of 0.45 eV.