Study of iodine diffusion in silicon carbide

Diffusion of iodine in 6H-SiC and polycrystalline CVD-SiC was investigated using Rutherford backscattering spectroscopy and electron microscopy. A fluence of 1 × 1016 cm−2 of 127I+ was implanted with an energy of 360 keV at room temperature, producing an amorphous surface layer of approximately 220 nm thickness. The implantation profile reached an atomic density of approximately 1.3% at the projected range of about 95 nm. Broadening of the implantation profile and iodine loss through the front surface during isochronal and isothermal vacuum annealing was determined. At a temperature of 1100 °C no iodine loss was observed after 120 h and a diffusion coefficient of less than 10−21 m2 s−1 was extracted from the analysis of profile widths. Relatively strong broadening occurred after 60 h annealing at 1200 °C with the iodine profile extending beyond 300 nm into the bulk, accompanied by a surprisingly modest iodine loss through the surface. Electron microscopic studies reveal a drastic restructuring of the surface region at this temperature, indicating possible chemical reactions between iodine and silicon carbide.