Carrier Diffusivity in Highly Excited Bulk SiC, GaN, and Diamond Crystals by Optical Probes

摘要

Optical monitoring of diffusivity in wide bandgap semiconductors was performed by using a picosecond light-induced transient grating technique. The bandgap renormalization and carrier-carrier scattering manifested themselves at room temperature as a two-fold decrease of the ambipolar diffusion coefficient D_a in cubic SiC and a 5-fold decrease of D_a in diamond at excess carrier density N > 10~(17) cm~(-3), while for GaN the impact was observed only at T < 100 K. For injections above 10~(19) cm~(-3), the plasma degeneracy led to enhanced D_a values in SiC and GaN and lessened the diffusivity decrease in diamond.