Process for growing active layers in sequence

A process for producing silicon carbide (SiC) substrates, comprising the steps of:

• (1) growing a first buffer layer (B1) on a substrate (S) using a first process gas comprising a first concentration of doping agent,
• (2) growing a first epitaxial layer (epi1) above said first buffer layer (B1) using a second process gas comprising a second concentration of doping agent,
• (3) growing a second buffer layer (B2) above said first epitaxial layer (epi1) using a third process gas comprising a third concentration of doping agent,
• (4) growing a second epitaxial layer (epi2) above said second buffer layer (B2) using a fourth process gas comprising a fourth concentration of doping agent.