Influence of radiation damage on krypton diffusion in silicon carbide

Diffusion of krypton in poly and single crystalline silicon carbide is investigated and compared with the previously obtained results for xenon, which pointed to a different diffusion mechanism than observed for chemically active elements. For this purpose 360keV krypton ions were implanted in commercial 6H-SiC and CVD-SiC wafers at room temperature, 350°C and 600°C. Width broadening of the implantation profiles and krypton retention during isochronal and isothermal annealing up to temperatures of 1400°C was determined by RBS-analysis, whilst in the case of 6H-SiC damage profiles were simultaneously obtained by α-particle channeling. Little diffusion and no krypton loss was detected in the initially amorphized and eventually recrystallized surface layer of cold implanted 6H-SiC during annealing up to 1200°C. Above that temperature thermal etching of the implanted surface became increasingly important. No diffusion or krypton loss is detected in the hot implanted 6H-SiC samples during annealing up to 1400°C. Radiation damage dependent grain boundary diffusion is observed at 1300°C in CVD-SiC. The results seem to indicate, that the chemically inert noble gas atoms do not form defect-impurity complexes, which strongly influence the diffusion behavior of other diffusors in silicon carbide.