Investigation of carrier lifetimes in a thin 4H-SiC epilayer

High-injection carrier lifetimes in thin 4H-SiC epilayers were investigated by using time-resolved photoluminescence method. It was found that the lifetimes in thin 4H-SiC epilayers were much shorter than that in relatively thick epilayers. Surface passivation using SiO₂ and SiN films, as well as numerical simulation based on a diffusion equation were performed in order to clarify lifetime limiting factors. A comparison between experimental and theoretical results reveals that the major cause of extremely short carrier lifetimes in thin 4H-SiC epilayers is short bulk lifetime rather than recombination at the epilayer surface or in the substrate.