Influence of radiation damage on strontium and iodine diffusion in silicon carbide

Abstract

The transport behaviour of strontium and iodine through single and polycrystalline SiC wafers was investigated using ion beam analysis and electron microscopy. Fluences of 2×1016 Sr+ cm−2 and 1×1016 I+ cm−2 were implanted at temperatures between 23°C and 600°C with an energy of 360keV, producing an atomic density of approximately 1.5% at the projected ranges of about 120nm and 90nm respectively. The broadening of the implantation profiles and its dependence on implantation parameters was determined by isochronal and isothermal annealing studies at temperatures up to 1400°C. The strong influence of radiation damage on diffusion after room temperature implantations was observed in all cases during the initial annealing stages at 1000°C. This is a result of the highly disordered crystal lattice, which re-crystallizes at this temperature. In hot implantations this effect is largely reduced but an additional transient diffusion process was observed at 1400°C for strontium, which is related to defect annealing. Impurity trapping by extended defects is obviously an important effect. Volume diffusion is below our detection limit of 10−21m2s−1 for both diffusors. Hence, grain boundary diffusion is responsible for the observed iodine transport in CVD-SiC at 1300°C, while no significant diffusion of strontium was detected at 1400°C.