The study of “Acceptor and donor impurity levels in hexagonal-diamond silicon” appeared in Phys. Rev. Materials 8, 114601 (2024).
The effect of p- and n-type substitutional doping on the structural and electronic properties of hexagonal-diamond Si (2H-Si) has been studied through ab initio DFT simulations. We have provided a detailed analysis of how a given impurity can assume a different local symmetry depending on the host crystal phase. Then, by studying neutral and charged dopants, we have carefully estimated donors’ and acceptors’ transition energy levels in 2H-Si and compare them with the cubic-diamond (3C) case. In the case of acceptors, the formation energy is always lower in 2H-Si and is associated with a shallower charge transition level with respect to 3C-Si. On the other hand, donors prefer the cubic phase and have transition energies smaller with respect to 2H-Si. Finally, by employing a simple model based on the 2H/3C band offset diagram, we have proven the physical validity of our findings and we have shown how holes can be used to stabilize the 2H-Si phase.
Reference: Marc Túnica, Alberto Zobelli and Michele Amato, Phys. Rev. Materials 8, 114601 (2024).