Diffusion of iodine in 6H-SiC and polycrystalline CVD-SiC was investigated using Rutherford backscattering spectroscopy and electron microscopy. A fluence of 1 x 1016/cm2 of 127I+ was implanted with an energy of 360keV at room temperature, producing an amorphous surface layer of approximately 220nm thickness. The implantation profile reached an atomic density of approximately 1.3% at the projected range of about 95nm. Broadening of the implantation profile and iodine loss through the front surface during isochronal and isothermal vacuum annealing was determined. At a temperature of 1100C no iodine loss was observed after 120h and a diffusion coefficient of less than 10−21m2/s was extracted from the analysis of profile widths. Relatively strong broadening occurred after 60h annealing at 1200C with the iodine profile extending beyond 300nm into the bulk, accompanied by a surprisingly modest iodine loss through the surface. Electron microscopic studies revealed a drastic restructuring of the surface region at this temperature, indicating possible chemical reactions between iodine and silicon carbide.

Study of Iodine Diffusion in Silicon Carbide. E.Friedland, N.G.van der Berg, J.B.Malherbe, R.J.Kuhudzai, A.J.Botha, E.Wendler, W.Wesch: Nuclear Instruments and Methods in Physics Research B, 2010, 268[19], 2892-6