Photogenerated carrier density dependence of ultrafast carrier dynamics in intrinsic 6H-SiC measured by optical-pump terahertz-probe spectroscopy

Ultrafast carrier dynamics and terahertz conductivity of intrinsic 6H-SiC are investigated by optical-pump terahertz-probe spectroscopy at room temperature. The amplitude of photoinduced absorption increases gradually and followed by a biexponential recovery with photogenerated carrier densities from 7.43 × 1017 to 2.81 × 1018 cm −3 at 400 nm. With the increase of photogenerated carrier density, the fast decay time decreases may be due to higher order recombination (i.e., Auger recombination), and the slow one increases is related to the band-filling effect. The evolution of complex conductivity with photogenerated carrier density at the delay time of about 50 ps can be better fitted with Drude–Smith​ model than Drude–Lorenz model. The Drude–Smith scattering time τDS and Smith​ parameter c1 increase with photogenerated carrier density implies carriers backscattering is dominant. Our analysis provides important basic data for research and improvement ultrafast semiconductor devices of intrinsic 6H-SiC.