Terahertz-emission generation caused by new effects in the 6H-SiC natural superlattice

It is demonstrated that the 6H-SiC natural superlattice has two simultaneously electroluminescence channels in the terahertz range: narrow lines at frequencies of 1.6–2.3 THz and broader lines at frequencies of about 3.25 THz. The first channel is formed by transitions between the localized states of the Wannier-Stark ladder in the Bloch oscillation mode in the first conduction miniband at point M of the hexagonal Brillouin zone. The second channel is probably caused by transitions between Wannier-Stark ladders formed by electric-field mixing of degenerate states of the conduction band at point K of the hexagonal Brillouin zone. The conduction-band minimum at point K is higher than that at point M by 100–200 meV.