Intrinsic Optical Absorption in Single-Crystal Silicon Carbide

The optical absorption of single-crystal silicon carbide has been measured in both the cubic and hexagonal, type $6H$, modification. The curves nearly coincide for absorption coefficients above ${10}^3$ ${\mathrm{cm}}^{-1\mathrm{}}$. At longer wavelengths the cubic structure absorbs more strongly. The absorption coefficient is 100 ${\mathrm{cm}}^{-1\mathrm{}}$ at 2.62 and 3.12 ev, respectively in these two crystals. The electron affinity of silicon carbide is estimated from photo-electric data to be about 4 ev.