The critical role of hydrocarbon source and growth optimization for high-quality thick 4H-SiC epitaxial layers

The development of ultra-high power electronic devices based on 4H-SiC relies on the growth of high-quality thick epitaxial layers. Chloride-based chemical vapor deposition is preferred for this purpose, and in this study we show that optimizing the process also requires a careful selection of hydrocarbons as the carbon source. Propane, a common precursor, limits control over the C/Si ratio at high growth rates, leading to defects and even loss of crystallinity. In contrast, methane offers a wider window for C/Si ratio adjustment, enabling further optimization of the epitaxial growth process. Using methane, an optimal growth rate of 25 μ m /h is identified at which the minority carrier lifetime is maximized. Additionally, a saturation limit for minority carrier lifetime is observed in layers exceeding a thickness of ∼ 100 μ m . It is also shown that, although the formation of characteristic surface morphological defects is inevitable, their severity can be controlled by adding additional HCl or increasing the growth rate; however, at a cost of reduced minority carrier lifetime. The growth of 125 μ m thick epitaxial wafers with methane and propane demonstrates the advantage of using methane as the carbon source. This is evidenced by a smoother surface, better doping uniformity, and nearly double the minority carrier lifetime compared to the propane-grown wafer. These findings highlight the benefits of methane in growing thick 4H-SiC epitaxial layers for high-power devices. • Study aims to optimize thick 4H-SiC epi-layer growth, vital for high-power devices. • Methane offers better C/Si ratio control than propane at high growth rates. • Methane yields smoother layers & longer MCL, crucial for device performance. • An optimal growth rate balances impurity incorporation & point defects for max MCL.