Abstract
The atomic geometries and transition levels of point defects and substitutional dopants in few-layer and bulk black phosphorus are calculated. The vacancy is found to reconstruct in monolayer P to leave a single dangling bond, giving a negative U defect with a +/− transition level at 0.24 eV above the valence band edge. The V− state forms an unusual 4-fold coordinated site. In few-layer and bulk black P, the defect becomes a positive U site. The divacancy is much more stable than the monovacancy, and it reconstructs to give no deep gap states. Substitutional dopants such as C, Si, O or S do not give rise to shallow donor or acceptor states but instead reconstruct to form non-doping sites analogous to DX or AX centers in GaAs. Impurities on black P adopt the 8-N rule of bonding, as in amorphous semiconductors, rather than simple substitutional geometries seen in tetrahedral semiconductors.
Highlights
The electronic structure of monolayer, few-layer, and bulk black phosphorus has been calculated by the screened exchange (sX) hybrid functional
The lack of doping effect means that black P might need to use work function control for best contacts, and not rely on doping to optimize contact resistances
The calculations are carried out using the plane-wave, density functional code CASTEP45
Summary
The electronic structure of monolayer, few-layer, and bulk black phosphorus has been calculated by the sX hybrid functional. The P vacancy is found to be a p-type defect lying 0.24eV above the VBM. The P vacancy is a negative U defect with + /− transition state for the monolayer P. For few layer and bulk P, the neutral state becomes more stable, and the vacancy becomes a positive U defect. The change of charge state will introduce significantly distortion to the lattice. The possible doping of O, S, C, and Si is considered. None of them could give p-type doping. The lack of doping effect means that black P might need to use work function control for best contacts, and not rely on doping to optimize contact resistances
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.