On the basis of first-principles calculations, an investigation was made of the total energies and electronic structures of 4H-SiC containing group-I (H, Li, Na, K, Rb) and group-VII (F, Cl, Br, I) elements as impurities. The favoured site, ionization energy and defect concentration for each impurity in 4H-SiC were determined. It was found that the formation energies of H and Li at interstitial sites were always lower than those at substitutional sites. In particular, for F and Na, a higher stability at either the interstitial or substitutional sites depended upon C-rich condition. The calculations revealed that interstitial F introduced a rather shallow acceptor level as well as conventional p-type dopants such as B and Al at substitutional Si sites. This suggested that interstitial F could be used to fabricate low-resistivity p-type SiC.

Electronic Structures of 4H-SiC with Group I and VII Elements: First-Principles Study of Possible p-Type Doping. M.Miyata, S.Hattori, Y.Hayafuji: Japanese Journal of Applied Physics, 2009, 48[4], 041301