Fabrication of high-quality nanobeam photonic crystal cavities in 4H silicon carbide with embedded color centers

A wide band-gap semiconductor with a long history of growth and device fabrication, silicon carbide (SiC) has attracted recent attention for hosting several defects with properties similar to the nitrogen vacancy center in diamond. In the 4H polytype, these include the silicon vacancy center and the neutral divacancy, which have zero phonon lines (ZPL) in the near-IR and may be useful for quantum information and nanoscale sensing. For many such applications, it is critical to increase the defect emission into the ZPL by coupling the emission to an optical cavity. Accordingly, we have pursued the fabrication of high quality 1D nanobeam photonic crystal cavities (PCCs) in 4H-SiC, using homoepitaxially grown material and a photoelectrochemical etch to provide optical isolation. These PCCs are distinctive in their high theoretical quality factors (Q > 106) and low modal volumes (V < 0.5 (λ/n)3). Here, we present arrays of nanobeam PCCs with varied lattice constant containing embedded silicon vacancy defects generated by electron irradiation, to assess its viability as a method for defect creation. The lattice constant variation allows us to create devices with modes spanning the entire range of the silicon vacancy emission. We accordingly demonstrate nanobeam PCCs with resonant modes near both ZPLs of the silicon vacancy defect. Moreover, we measure devices with the highest Q cavity modes coupled to point defect emission in SiC yet reported, providing evidence that electron irradiation can be used to generate point defects while maintaining high quality optical devices.