Role of anion-cation antisites in Zn-based II-IV-V₂ chalcopyrite semiconductors

Since the order-disorder phase transition easily occurs during the growth of optoelectronic II-IV-V₂ ternary compounds, cation-cation antisites were always considered as the major point defects, while anion-related defects did not attract sufficient attention. In this paper, based on first-principles simulations, the anion-cation antisites are revealed to be comparable to or even dominate over the cation-cation antisites in II-IV-V₂ phosphides and arsenides. These antisite defects are predicted to have significant impacts on the optoelectronic properties because they can either act as nonradiative recombination centers or enhance the p-type carrier concentration. Furthermore, based on the calculated defect properties and band alignments, we propose that the alloy ZnGe(P,As)₂ can be an efficient p-type solar cell absorber. Its maximal open circuit voltage is effectively enlarged by the low valence band edge; meanwhile, the dominating anion-cation antisites are electrically benign. These results highlight the necessity of considering the anion-cation antisites in the defect engineering of II-IV-V₂ phosphides and arsenides.