Native defects in Tl₆SI₄: Density functional calculations

Tl₆SI₄ is a promising roomerature semiconductor radiation detection material. Here, we report density functional calculations of native defects and dielectric properties of Tl₆SI₄. Formation energies and defect levels of native point defects and defect complexes are calculated. Donor-acceptor defect complexes are shown to be abundant in Tl₆SI₄. High resistivity can be obtained by Fermi level pinning by native donor and acceptor defects. Deep donors that are detrimental to electron transport are identified and methods to mitigate such problem are discussed. Furthermore, we show that mixed ionic-covalent character of Tl₆SI₄ gives rise to enhanced Born effective charges and large static dielectric constant, which provides effective screening of charged defects and impurities.