Decrease in Al acceptor density in Al-doped 4H-SiC by irradiation with 4.6 MeV electrons

From the temperature dependence of the hole concentration $\mathrm{p(T)}$ in a lightly Al-doped 4H-SiC epilayer, an Al acceptor with $\text{∼200\hspace{0.17em}}\mathrm{meV}$ and an unknown defect with $\text{∼370\hspace{0.17em}}\mathrm{meV}$ are found. By irradiation with 4.6 MeV electrons, the Al acceptor density is reduced, while the unknown defect density is almost unchanged. This indicates that the substitutional Al atoms in 4H-SiC are displaced by irradiation or that the bonds between the substitutional Al atom and the nearest neighbor atom are broken by irradiation. Moreover, the reduction in $\mathrm{p(T)}$ with irradiation arises from the decrease of the Al acceptors, not from the formation of hole traps or donor-like defects.