First-principles calculations of p-type impurities in cubic SiC

The electronic structures, atomic geometries, formation energies, and ionization energies of the substitutional Al and B in cubic SIC are calculated by the first-principles pseudopotential method. It is shown from the calculations of the ionization energies that both Al and B form a shallow acceptor level on a Si site and a deep level on a C site. For Al, a Si site has a lower formation energy than a C site regardless of the composition, while for B, the lower formation energy site depends on the composition. A C site is favorable for B under Si-rich conditions and a Si site under C-rich conditions. These results suggest that the low-resistivity p-type SiC crystal can be fabricated under C-rich conditions when B is employed as a dopant.