Theoretical study of Cl-related defect complexes in cubic SiC

Abstract

First-principles calculations were employed to investigate the electronic properties and formation energy of Cl-related complex defects, with either carbon (silicon)vacancies, V[C] (V[S ]i ) or dopants (nitrogen/aluminum). Our investigation revealed that Cl at a Si-site related complexes, such as the Cl[Si]V[C] and Cl[Si]N[C] , are either structurally unstable or possess a rather high formation energy, in agreement with the fact that Cl energetically favors a C-site. By employing the defect-molecule model, we found that Cl[C]V[S i] and Cl[C]Al[Si] complexes have C[3v] symmetry and are both donors. However, contrarily to the case of the Cl[C]V[S i] complex, for the Cl[C]Al[Si] complex the singlet (A[1]) orbitals can lie higher in energy position than the doubly degenerate orbital (E). The formation energies of Cl-vacancy/dopant complex defects are discussed in the light of recent experimental results, reported for 4 H-SiC grown by Cl-based chemical vapor deposition.