The zero-phonon lines, phonon sidebands and the dynamics of optically induced spin polarization of the neutral divacancies ${\left({\mathrm{V}}_{\mathrm{Si}}{\mathrm{V}}_{\mathrm{C}}\right)}^{\circ }$ in $4H\text{−}\mathrm{SiC}$ have been investigated by EPR spectroscopy. Via in-situ resonant optical excitation at $T=4\mathrm{K}$ the zero phonon lines (ZPL) between the ${}^3{\mathrm{A}}_2$ groundstate and the ${}^3\mathrm{E}$ excited states and their absorption phonon side bands (PSB) have been accurately determined for each of the four ${\mathrm{VV}}^{\circ }$ centers (hh, kk, kh, hk) from the spectral dependence of the EPR line intensity. Their values, respectively 1130.7 nm (hh), 1129 nm (kk), 1107.5 nm (kh) and 1077.3 nm (hk) are in good agreement with previous PL studies and with theoretical predictions. Decomposition of the phonon sidebands of the basal VV centers reveals a coupling with phonons of 24, 36, and 47.5 meV $\left({\mathrm{V}}_{\mathrm{kh}}\right)$ and 11.5, and 18.6 meV $\left({\mathrm{V}}_{\mathrm{hk}}\right)$. The low-temperature optical excitation of the ${\mathrm{VV}}^{\circ }$ centers gives rise to a 100% ground-state spin polarization which persists at $T=4$ K for hundreds of seconds, when the excitation is switched off. Contrary to the case of VV centers in $n$-type nitrogen doped $4H\text{−}\mathrm{SiC}$, the VV centers in $p$-type doped 4H-SiC do not show any charge-state instability under optical excitation.

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• Defects
• Electron-phonon coupling
• Spin polarization
• Semiconductors
• Density functional calculations
• Electron paramagnetic resonance