Single silicon vacancies V_Si in silicon carbide nanostructures hold great promise for future technological applications in scalable quantum computing and information processing for simulation, sensing, and communication. These defects are typically created by ion implantation or neutron/electron irradiation. Identification of these defects, knowledge of their characteristics, control of their concentrations, isolation of single spin defects and understanding the effects of semiconductor processing on their properties are crucial to the applications of SiC in quantum electronic and integrated photonic devices. These vacancies embedded in photonic crystal cavities (PCC) have the capability of high efficiency emission of single photons which can significantly improve the performance of on-chip photonic networks and long-distance quantum communication systems, as compared to conventional solid-state emitters. Here we investigate the impact of processing on the photoluminescence properties of PCCs fabricated using three approaches: hydrogen implantation to form thin SiC layers on an oxide layer that can be easily etched away to form an air gap under the PCC, wafer bonding and mechanical thinning of the SiC, also on an oxide layer, and selective photo-electrochemical etching of an n-p epitaxial SiC structure to form an air gap. We also assess the impact of electron irradiation for these three fabrication approaches.