Carrier diffusion characterization in epitaxial 4H-SiC

Carrier diffusivity has been experimentally determined in low-doped n-type epitaxial 4H-SiC over a wide injection range using a Fourier transient grat ing technique. The data showed that, with injection, the diffusion coeffici ent increased from a minority-hole diffusivity D-h = 2.3 cm(2)/s to an ambi polar diffusivity D-a = 4.2 cm(2)/s at approximately 10(16) cm(-3) with a s ubstantial decrease occurring at higher injections. The derived D-h value c orresponded to a minority-hole drift mobility of mu (h) = 90 cm(2)/Vs, abou t 30% lower than available majority-hole mobilities. Also. the temperature dependence of the ambipolar diffusivity in the 296-523 K range has been det ermined. It followed a power law D-a similar to T-1.3 which notably differe d from the expected one using the majority-hole mobility temperature depend ence.