Enhanced cavity coupling to silicon vacancies in 4H silicon carbide using laser irradiation and thermal annealing.

ABSTRACT

The negatively charged silicon monovacancy [Formula see text] in 4H silicon carbide (SiC) is a spin-active point defect that has the potential to act as a qubit in solid-state quantum information applications. Photonic crystal cavities (PCCs) can augment the optical emission of the [Formula see text], yet fine-tuning the defect-cavity interaction remains challenging. We report on two postfabrication processes that result in enhancement of the [Formula see text] optical emission from our PCCs, an indication of improved coupling between the cavity and ensemble of silicon vacancies. Below-bandgap irradiation at 785-nm and 532-nm wavelengths carried out at times ranging from a few minutes to several hours results in stable enhancement of emission, believed to result from changing the relative ratio of [Formula see text] ("dark state") to [Formula see text] ("bright state"). The much faster change effected by 532-nm irradiation may result from cooperative charge-state conversion due to proximal defects. Thermal annealing at 100 °C, carried out over 20 min, also results in emission enhancements and may be explained by the relatively low-activation energy diffusion of carbon interstitials [Formula see text], subsequently recombining with other defects to create additional [Formula see text]s. These PCC-enabled experiments reveal insights into defect modifications and interactions within a controlled, designated volume and indicate pathways to improved defect-cavity interactions.