N-type B-S co-doping and S doping in diamond from first principles

The S-doped diamond and B-S co-doped diamond at different concentrations were investigated by the density functional theory (DFT) to explore the possibility to achieve effective and shallow donors in diamond. We found for the first time that the Valence Band maximum (VBM) and the Intermediate Band (IB) minimum of B-S co-doped diamond are located at the same κ-point Γ, which is quite different from the indirect energy gap of S-doped diamond and pure diamond. Although the simulated ionization energy of B-S defect is deeper than that of S defect, the impurities formation energy is much lower than that of S defect. It suggests that the introduction of B help improve the solubility of S in diamond. Besides, the electron effective mass of IB of B-S co-doped diamond is much smaller than that of the S-doped diamond, which may lead to conductivity promotion for diamond. Comparison of the density of states in both cases, it is found that the S-3p states are responsible for conduction band, as well as the B-2p states of B-S co-doped diamond have a little contribution to its conduction band. It can conclude that with the assistance of B, S is a suitable shallow donor impurity in diamond.