Terahertz conductivity and ultrafast dynamics of photoinduced charge carriers in intrinsic 3C and 6H silicon carbide

The terahertz conductivity of photoinduced charge carriers in two common polytypes of silicon carbide, 3CSiC and 6H-SiC, is studied on picosecond timescales using an optical-pump/ THz-probe technique. We find that the conductivity, measured from 0.7 to 3THz, is well described by the Drude model, and obtain a velocity relaxation time of 75 fs, independent of sample and charge-carrier density. In contrast, the carrier relaxation rates in the two polytypes differ by orders of magnitude: in 6Hand 3C-SiC, recombination proceeds on a time scale of few picoseconds and beyond nanoseconds, respectively.