Formation preference of divacancy ensemble in 4H-SiC

The divacancy ensemble in 4H silicon carbide (4H-SiC) is a promising spin-defect candidate for quantum sensing and scalable quantum technologies. The ability to fabricate well-defined divacancy ensembles is essential for practical implementation. In this work, the formation characteristics of divacancy ensembles are systematically investigated. First, a strong host dependence of divacancy formation is observed. The high purity semi-insulating (HPSI) 4H-SiC substrates yield high divacancy concentrations, followed by the epitaxial layer, whereas the formation is significantly suppressed both in the heavily doped n-type and p-type substrates. Second, the fabrication process exhibits remarkable selectivity among different divacancy configurations. The photoluminescence intensities of PL1 and PL2 centers dominate the ensemble in all suitable hosts among types of hosts with isochronal annealing comparison. The migration of silicon vacancy dominates the formation of divacancy, whose migration barrier is tuned by Fermi level. It also confirms that the electron irradiation and annealing process is a general routine to fabricate divacancy ensembles. Third, the PL5 ensemble is only observed in a specific host with various treatments. The formation of PL5 is strongly linked to the specific point defects with high formation barriers, rather than stacking faults, which makes it feasible to fabricate PL5 ensembles with uniform spatial distribution. Finally, magnetic response of PL1 ensemble is achieved at room temperature successfully. Its structural characteristics eliminate the need of additional bias magnetic field for resonant degeneracy. This work offers a new insight into defect engineering in wide-bandgap semiconductors. It also provides a reliable fabrication strategy for tailored divacancy ensembles in 4H-SiC and advances their potential for practical quantum sensing applications.