Comparative study of divacancies in 3C-, 4H-, and 6H-SiC

The divacancy comprising two neighboring vacant sites in the SiC lattice is a promising defect for applications in quantum technology. So far, most research has focused on the divacancy in 4H-SiC, whereas the divacancies in 6H- and 3C-SiC have received much less attention. Here, we outline arguments showing that the neutral charge state of the divacancies in the latter two polytypes is intrinsically stable, in contrast to that in 4H-SiC, where the photoluminescence quenches in most materials for certain excitation energies (below approximately 1.3 eV). Divacancies in 6H- and 3C-SiC are anticipated to remain stable for all excitation energies above resonant excitation. We provide ab initio calculation results for the charge transfer levels of divacancies in 6H- and 3C-SiC. We also show that the luminescence from the divacancy in 3C-SiC vanishes with increasing temperature toward room temperature because of the proximity of the excited state to the conduction band.