Comparison of the annealing behavior of high-dose nitrogen-, aluminum-, and boron-implanted 4H–SiC

Room temperature free carrier concentrations exceeding ${\text{1×10}}^{18}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-1}}$ have been achieved with 1000 °C implants into 4H–SiC using N and Al (${\text{1×10}}^{17}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}}$ using B). A decrease in resistivity is observed for annealing temperatures above $\text{∼1300,}$ $\text{∼1500,}$ and $\text{∼1750\hspace{0.17em}°}\mathrm{C}$ for N, Al, and B, respectively. Rutherford backscattering spectroscopy measurements indicate almost complete recrystallization for N-implanted samples and partial recrystallization on the silicon, but not the carbon, sublattice for B- and Al-implanted samples. An implant and species related step formation is also observed. Only boron is observed to diffuse appreciably. A crystal stoichiometry and Fermi level dependent model is proposed to explain the activation results.