In FIG. 2, the vanadium concentration [/cm3] of the silicon carbide epitaxial layer is shown on a horizontal axis and the carrier lifetime τ of the silicon carbide epitaxial layer is shown on a vertical axis as 1/T (an inverse of the carrier lifetime τ) [μs?1]. In FIG. 2, “no doping” on the horizontal axis indicates that vanadium is not doped in the silicon carbide epitaxial layer. Further, in FIG. 2, the greater is the value on a vertical axis, the shorter is the carrier lifetime τ of the silicon carbide epitaxial layer. Substrate temperature T during lifetime measurement is 20 degrees C. The substrate temperature is the temperature of the semiconductor substrate 10.
FIG. 3 is a characteristics diagram depicting a relationship between the n-type doping concentration and the vanadium concentration of the n-type silicon carbide epitaxial layer. In FIG. 3, the vanadium concentration [×1013/cm3] of the n-type silicon carbide epitaxial layer is shown on a horizontal axis and a doping concentration [×1015/cm3] of the n-type silicon carbide epitaxial layer is shown on a vertical axis. The doping concentration of the n-type silicon carbide epitaxial layer is a concentration difference (=Nd—Na) obtained by subtracting an acceptor concentration (acceptor density) Na from donor concentration (donor density) Nd of the n-type silicon carbide epitaxial layer. The conductivity type of the n-type silicon carbide epitaxial layer is an n-type and therefore, in the n-type silicon carbide epitaxial layer, the donor concentration Nd is higher than the acceptor concentration Na (Nd—Na>0).
