Enhanced annealing of the Z1∕2 defect in 4H–SiC epilayers

The authors investigated the application of the carbon-implantation/annealing method for the annealing of the main lifetime limiting defect $Z_{1∕2}$ in thick 4H–SiC epilayers. Examination of different implantation doses and annealing temperatures showed that finding the optimum conditions is crucial for obtaining thick layers with carrier trap concentration below ${10}^{11}{\mathrm{cm}}^{-3}$ in the whole $100\mu \mathrm{m}$ epilayer. The carrier lifetime increased from less than $200\mathrm{ns}$ to over $1\mu \mathrm{s}$ at room temperature in the samples annealed with the carbon-implanted layer. The thick 4H–SiC epilayers after the application of the carbon-implantation/annealing were confirmed to be applicable for fabrication of high-voltage bipolar devices and resulted in improved conductivity modulation. Possible annealing mechanisms are discussed in detail making a comparison between annealing of as-grown material and irradiated material.