Reduction of traps and improvement of carrier lifetime in 4H-SiC epilayers by ion implantation

The authors report a significant reduction in deep level defects and improvement of carrier lifetime in $4H\text{-}\mathrm{Si}\mathrm{C}$ material after carrying out carbon or silicon ion implantation into the shallow surface layer of $250\mathrm{nm}$ and subsequent annealing at $1600°\mathrm{C}$ or higher temperature. Reduction of $Z_{1∕2}$ and ${\mathrm{EH}}_{6∕7}$ traps from $3\times {10}^{13}{\mathrm{cm}}^{-3}$ to below the detection limit $(5\times {10}^{11}{\mathrm{cm}}^{-3})$ was observed by deep level transient spectroscopy in the material $4\mu \mathrm{m}$ underneath the implanted layer. Minority carrier lifetime almost doubled in the implanted samples compared to the unimplanted samples. The authors propose that the implanted layer acts as a source of carbon interstitials which indiffuse during annealing and accelerate annealing out of grown-in defects in the layer underneath the implanted region.