Free carrier absorption and lifetime mapping in 4H SiC epilayers

Results of carrier lifetime studies in low-doped epitaxial 4H SiC layers are reported. The free carrier absorption (FCA) technique was applied to extract carrier lifetime parameters and their spatial distribution in a wide photoexcitation range. The FCA magnitude is shown to scale linearly with the photoinjected carrier concentration, while the absorption cross section increases according to a λ4.4 law for near infrared wavelengths. High spatial resolution carrier lifetime mapping of large 4H SiC areas revealed features related to structural imperfections of epilayers. Finally, a density dependent fast lifetime component was observed at high injection levels and attributed to band-to-band Auger recombination.