The forefront of semiconductor silicon carbide technology now approaches commercialization for both materials and device technology. The commercialization of SiC epitaxy processes requires improvement in defect density, uniformity and repeatability. Especially problematic are graphite particles, gas phase nucleation of particles and the limitations placed on achieving growth rates that can positively impact process costs. When it approached the same historical point of development, silicon epitaxy technology shifted to the use of chlorosilane precursor gases to suppress gas phase nucleation and achieve targeted growth rates. Recent work on SiC epitaxy chemistry now investigates the use of HCl, halocarbons and most recently chlorosilane precursors. This paper will review the original work on gas phase nucleation and its control in silicon epitaxy processes using HCl additives and chlorosilanes. Using established dissociation pathways for chlorosilanes, equilibrium chemical reaction models are used to assess the impact of HCl, halocarbons and chlorosilane precursors on growth rates and particle formation SiC epitaxy. Experimental data is presented on the comparative performance of HCl additive and chlorosilane precursors in SiC epitaxy and film properties.