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

Abstract

The negatively charged silicon monovacancy VSi− 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 VSi−, yet fine-tuning the defect–cavity interaction remains challenging. We report on two postfabrication processes that result in enhancement of the V1′ 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 VSi0 (“dark state”) to VSi− (“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 Ci, subsequently recombining with other defects to create additional VSi−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.

Photonic crystal nanobeam cavities based on 4H-silicon carbide on insulator

“…The PhC cavity with a = 270 nm exhibits a Q-factor of 2.8 × 10 3 , while the PhC cavity with a = 290 nm exhibits a much higher Q-factor of 6.2 × 10 3 . The high Q-factor of 6.2 × 10 3 obtained in our work is on a par with the previously reported nanobeam cavities fabricated with bulk 4H-SiC material [19,31] .…”

Defect-Induced Luminescence Quenching of 4H-SiC Single Crystal Grown by PVT Method through a Control of Incorporated Impurity Concentration

“…The 4H-SiC structure has been shown to have several defects and PL peaks in the band gap. The PL spectra in 4H-SiC originate from a combination of phonon-instigated electronic transitions caused by defects in SiC [9][10][11]. This observation of luminescence quenching is not evidence of electronic doping [12,13].…”

Designing silicon carbide heterostructures for quantum information science: challenges and opportunities

“…Embedding optically active point defects in nanophotonic structures with high quality factors is a promising path toward optimizing color center optical emission rates for quantum technologies [169,170,201]. However, the extreme sensitivity of both the color centers and cavity modes to the quality of the surrounding material leads to losses in spin-photon coupling efficiency in cavities with fabrication-related imperfections [165,167,169,183,184,[201][202][203]. Heteropolytypic SiC materials promise to meet the demand for superior device fabrication techniques by enabling new and less damaging polytype-selective wet etching protocols [138,182].…”