Characterization of SiC crystals by optical and electrical means

Measurements of carrier transport have been carried out in different SiC polytypes by using two complementary techniques: a picosecond four-wave mixing and magnetoresistance. Both techniques confirmed the mechanism of phonon scattering in T = 100-300 K range, as well as higher carrier mobility in n-type 4H epitaxial layers with respect to 3C-SiC. The optical technique revealed a decrease of the bipolar mobility in 3C-SiC at T < 100 K and its variation with photoexcited carrier density. A lattice heating was observed in free standing 3C- and 4H-SiC due to strong impact of nonradiative recombination, and this effect precluded optical studies of carrier dynamics at low temperatures.