Stability and electronic properties of planar defects in quaternary I₂-II-IV-VI₄ semiconductors

Extended defects such as stacking faults and anti-site domain boundaries can perturb the band edges in Cu₂ZnSnS₄ and Cu₂ZnSnSe₄, acting as a weak electron barrier or a source for electron capture, respectively. In order to find ways to prohibit the formation of planar defects, we investigated the effect of chemical substitution on the stability of the intrinsic stacking fault and metastable polytypes and analyzed their electrical properties. Substitution of Ag for Cu makes stacking faults less stable, whereas the other substitutions (Cd and Ge) promote their formation. Ge substitution has no effect on the electron barrier of the intrinsic stacking fault, but Cd substitution reduces the barrier energy, and Ag substitution enhances electron capture by the stacking fault. While Cd substitution stabilizes the stannite structure, chemical substitutions make the primitive-mixed CuAu structure less stable with respect to the ground-state kesterite structure.