Effect of chemical substitution on polytypes and extended defects in chalcopyrites: A density functional theory study

In ternary semiconductors, both stacking disorder and cation disorder can cause the formation of polytypes and extended defects. We perform density functional theory calculations to investigate the stability of polytypes in six ternary sulfides, such as CuIn S 2, CuGa S 2, CuAl S 2, AgIn S 2, AgGa S 2, and AgAl S 2. The formation energy of polytypes generated by stacking disorders is used to generate the anisotropic next-nearest neighbor Ising models. The estimated stacking fault energy by the model is in good agreement with the calculated stacking fault energy. The incorporation of Ga and Ag tends to suppress and promote the formation of stacking faults, respectively. On the other hand, the electronic bandgap of the polytypes generated by cation disorder is negatively correlated with the formation energy, resulting in the trapping of charge carriers at antisite domain boundaries. The formation of antisite domain boundaries can be suppressed by the incorporation of Ag and Ga.