Bonding mechanisms and electronic properties of HgIn2Te4 with Au doping: First-principles study.

HgIn₂Te₄ (Mercury indium telluride, MIT) is a promising mid-infrared CO₂ laser candidate material. Through combining the calculation results of structural relaxation, Bader charge, electronic localization function, formation energy, and density of states, we systematically explored the stability and doping efficiency of gold (Au) in MIT. The results show that the Au-Te bond has a similar polar covalent characteristic as Hg-Te bond, which indicates the relative stability of Au dopant in MIT. In addition, two defect states were formed through the hybridization between the Au impurity and its nearest neighboring Te atoms in the substitutional doping systems of Au_Hg and Au_In. We found that the acceptor transition levels in Au_Hg and Au_In are 0.095 eV and 0.265 eV above the valance band maximum, respectively, whereas the donor transition level in the substitutional doping system of Au_Te and interstitial system of Au_I are 0.894 eV and 0.322 eV below the conduction band minimum, respectively. Meanwhile, in the Hg-rich condition, the Fermi level would be pinned about 0.511 eV above the valence band maximum due to the self-compensation effect; however, this effect will be efficiently reduced in the Te-rich condition. [ABSTRACT FROM AUTHOR]