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.