Nanostructuring of SiC for novel defect-based quantum technologies

Point defects in semiconductors have emerged as viable candidates for quantumbased technologies such as quantum computing, communication, and sensing. The present work is related to quantum compatible point defects in silicon carbide (SiC), particularly the silicon vacancy, a point defect and material system that has received considerable research interest in the last few years. In this thesis, a fabrication process was developed for producing structures in SiC that can be used as, e.g., waveguides for single-photon emission. This was performed by depositing a SiO2 layer with plasma chemical vapor deposition (PECVD) on a high purity 4H-SiC wafer. Next, with photolithography, the SiO2 layer was patterned with a photoresist mask in a reactive ion etching (RIE) step. The patterned SiO2 layer was then used as a hard mask for a subsequent RIE step, finalizing the photonic device. A thin nickel layer was deposited on the structures with physical vapor deposition (PVD) for the charge-state control through a liftoff process with a photoresist mask. Defect creation was achieved by 21 keV He implantation to a fluence of 1×1011 cm−2 with an ion implanter. In a scanning electron microscope (SEM), the device morphology showed sharply defined features with almost vertical sidewalls. The diffraction limit from the photolithography resulted in increasingly tilted sidewalls as the structures decreased in size. The optical properties were characterized with cathodoluminescence (CL) spectroscopy and exhibited emission in the V1 and V1’ zero-phonon lines (ZPLs) associated with the VSi. Charge-state control of the VSi was identified by enhancing the V− Si CL emission intensity in the depletion region of the Schottky contact, with a reduction in intensity towards the depletion region edge. By utilizing angle-resolved cathodoluminescence (ARCL) spectroscopy, the radiation profiles of the photonic structures were shown to be altered compared to the Lambertian radiation profile of the implanted wafer. Though no electromagnetic wave propagation in discrete modes (waveguiding effect) was observed, the photonic devices enhanced the emission intensity of the VSi in all directions by functioning as a lens with a higher numerical aperture than the wafer, and the lens had characteristics similar to a combination of a solid immersion lens (SIL) and an optical fiber. The findings presented herein are important for further photonic device fabrication in 4H-SiC, and lay the groundwork for incorporating quantum compatible point defects in electrically driven quantum technology devices