Towards Identifying the PL6 Center in SiC: From First-Principles Screening to Hyperfine Validation of Competing Defect Candidates

Abstract

The PL6 color center in 4H-SiC, known for its excellent ambient-temperature spin and optical properties, has an unresolved microscopic origin. In this first-principles study, we systematically investigate potential structures to clarify its nature. We first rigorously examine the DV-antisite hypothesis (a divacancy paired with a carbon antisite, $\mathrm{C_{Si}}$), analyzing the energetic, electronic, and spin properties of various $V_\mathrm{Si}V_\mathrm{C}+\mathrm{C_{Si}}$ configurations. Two $\mathrm{C_{3v}}$-symmetric $\mathrm{kk+C_{Si}}$ complexes emerge as strong candidates within this framework. Subsequently, a critical comparison of hyperfine interaction signatures is performed between these candidates, the alternative OV model [specifically OV(hh) and OV(kk), an oxygen replacing C together with a Si vacancy], and experimental data. This analysis demonstrates that the OV(hh) structure more accurately reproduces PL6's hyperfine features. Furthermore, re-evaluation of the proposed OV(hk) model for the related PL5 center reveals zero-field splitting parameter $E$ inconsistencies with experimental results, suggesting that PL5 and PL6 may have distinct origins. These findings provide crucial theoretical insights and motivate targeted experimental validation for these quantum defects.

Figures (3)

• Figure 1: The structure, sites of 4H-SiC. (a) The local structure of a kk divacancy, illustrating important sites giving rise to hyperfine signatures typical for c-axis aligned defects in (a). (b) The top view of the plane containing the $V_\mathrm{Si}$, for better illustration of the labeled sites. In (a,b), the important sites are marked with different colors, and the label also adopts the same color. (c) Stacking order of atomic layers (h for hexagonal, k for cubic) along the c-axis in 4H-SiC, illustrating schematic examples of a $V_\mathrm{Si}V_\mathrm{C}$(kk) divacancy and an $\mathrm{O_C}V_\mathrm{Si}$(hk) defect.
• Figure 2: Atomic structure of the $\mathrm{kk+ C_{Si}(0, 0, \overline{8})}$ and $\mathrm{kk+ C_{Si}(0, 0, 8)}$ DV-antisite complexes. These configurations emerged as compelling candidates for the PL6 center from the screening of $V_\mathrm{Si}V_\mathrm{C}$+$\mathrm{C_{Si}}$ structures. The kk divacancy is shown as blue dotted circle, and the ${\rm C_{Si}}$ antisite defect is shown in black.
• Figure 3: The distribution of the $A_{zz}$ component for the kk, hh, $\mathrm{kk+ C_{Si}(0, 0, 8)}$ and OV(hh), OV(kk) defects. The smooth curve represents the sum of Gaussian distributions, with a mean value given by $A_{zz}$ and a standard deviation of 0.5 MHz. The gray shaded regions correspond to the experimentally observed $\mathrm{Si_{IIa}}$ and $\mathrm{Si_{IIb}}$ hyperfine splitting sites. And the isotopic abundances of ${\rm ^{29}Si}$ and ${\rm ^{13}C}$ are also taken into account. For clearer individual presentations of these comparisions, Fig. \ref{['hyper_stat']}(b)-Fig. \ref{['hyper_stat']}(d) in the Supplemental Material suppl each plot the $A_{zz}$ distribution of a specific key defect alongside those of hh and kk.