The self-diffusion of 12C and 13C in weakly-doped (intrinsic) 4H material was studied by using secondary ion mass spectrometry. Two-layer 13C enriched structures, with 13C/12C ratios of 0.01 and 0.1, were prepared by vapour phase epitaxy. Subsequent annealing was carried out in an Ar atmosphere in a radio-frequency heated furnace at between 2100 and 2350C for 0.25 to 40h. The 13C depth profiles revealed a strict √t evolution of the diffusion, and the deduced C self-diffusion coefficients (figure 28) closely obeyed the Arrhenius dependence:

D (cm2/s) = 8.4 x 102 exp[-8.50(eV)/kT]

The D-values were 5 orders of magnitude lower than those previously reported, at the same temperatures, in 14C radiotracer experiments.

Self-Diffusion of 12C and 13C in Intrinsic 4H–SiC. M.K.Linnarsson, M.S.Janson, J.Zhang, E.Janzén, B.G.Svensson: Journal of Applied Physics, 2004, 95[12], 8469-

Figure 28

Diffusivity of 13C in 4H-SiC