Manifestation of intrinsic defects in the band structures of quaternary chalcogenide Ag2In2SiSe6 and Ag2In2GeSe6 crystals

Abstract

Complex studies on the band structures of novel Ag₂In₂SiSe₆ and Ag₂In₂GeSe₆ crystals were performed. Experimental and theoretical analysis of the manifestation of intrinsic vacancies, possessing cationic and anionic character, located in quaternary crystals was shown for the first time. The contribution of localized states to the band structure, optical absorption edge, effective mass, carrier mobility etc. was explored including both measurements of their polarized absorption fundamental edge as well as electronic property calculations within the framework of the DFT methodology. Therefore, the probability of the appearance of different types of defects was analyzed and the dispersion of the energy band possessing substantial carrier transport anisotropy was discussed. Silver vacancies were considered to particularly change the energy gap of both crystals by adding an acceptor level above the valence band. The proposed approach may be generalized for many chalcogenide complexes.