Nonequilibrium carrier recombination in highly excited bulk SiC crystals

We applied time-resolved free carrier absorption (FCA) to monitor non-equilibrium carrier dynamics in 4H epilayers and 3C SiC bulk crystals at excess carrier densities in the Delta N = 10(17) - 10(19) cm(-3) range. The numerical fitting of FCA decay kinetics provided the linear and nonlinear carrier recombination rates in the 40-390 K range and the absorption cross-sections sigma(eh) at 1064 nm. In 4H, the decrease of the bulk lifetime (800 us) with excitation provided the bimolecular and Auger coefficients B=(1.2 +/- 0.4)x10(-12) cm(3)/s and C=(7 +/- 4)x10(-31) cm(6)/s, respectively, at room temperature. These values for 3C were 55-150 us, (2.0 +/- 0.4)x10(-12) cm(3)/s, and (2 +/- 1)x10(-32) cm(6)/s, respectively. The rate of linear and nonlinear recombination increased at lower temperatures. A value of sigma(eh) =44x10(-18) cm(2) for 3C SiC at 1.064 mu m was found 2.3 times smaller than that for 4H SiC.