Electrically active point defects in n-type 4H–SiC

Abstract

An electrically active defect has been observed at a level position of $\text{∼0.70\hspace{0.17em}}\mathrm{eV}$ below the conduction band edge ${\mathrm{(E}}_c)$ with an extrapolated capture cross section of ${\text{∼5×10}}^{\text{−14}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{2}}$ in epitaxial layers of $4\mathrm{H–SiC}$ grown by vapor phase epitaxy with a concentration of approximately ${\text{1×10}}^{13}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}}.$ Secondary ion mass spectrometry revealed no evidence of the transition metals Ti, V, and Cr. Furthermore, after electron irradiation with 2 MeV electrons, the 0.70 eV level is not observed to increase in concentration although three new levels are observed at approximately 0.32, 0.62, and 0.68 eV below $E_c$ with extrapolated capture cross sections of ${\text{4×10}}^{\text{−14}},$ ${\text{4×10}}^{\text{−14}},$ and ${\text{5×10}}^{\text{−15}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{2}},$ respectively. However, the defects causing these levels are unstable and decay after a period of time at room temperature, resulting in the formation of the 0.70 eV level. Our results suggest strongly that the 0.70 eV level originates from a defect of intrinsic nature. The unstable behavior of the electron irradiation-induced defects at room temperature has not been observed in the $6\mathrm{H–SiC}$ polytype.