Influence of different hydrocarbons on impurities and minority carrier lifetime in 4H-SiC epitaxial layers

This study explores the influence of different hydrocarbons, methane and propane, on the properties of 4H-SiC epitaxial layers grown by chloride-based chemical vapor deposition. By systematically varying the C/Si and N/C ratios during epitaxial growth, and employing a comprehensive suite of characterization techniques, a better understanding of how growth conditions influence material properties is gained. We show that the n-type dopant incorporation strongly depends on the choice of hydrocarbon especially at lower doping levels. Furthermore, we have observed that methane contributes to a relatively longer carrier lifetime value compared to propane, though a similar lifetime limiting carbon vacancy defect concentration has been observed for both hydrocarbons in as-grown epitaxial layers. Moreover, additional defect levels are also suggested by deep-level transient spectroscopy, potentially related to chlorine complexes, with varying concentrations depending on the choice of hydrocarbon and C/Si ratio. These observations offer insights into the complicated interplay of factors influencing doping, minority carrier lifetime, and defect formation in 4H-SiC epitaxial layers during the epitaxial growth process, and contribute to the optimization of growth parameters depending on the application in question.