Electronic structure of silicon carbide polytypes studied by soft X-ray spectroscopy

The electronic structure of SiC polytypes is investigated with soft x-ray a bsorption (SXA) and emission (SXE) spectroscopy studying the local C p and Si (sf d) partial density of states (LPDOS) of it-doped cubic 3C-SiC and he xagonal 4H- and 6H-SiC. The shape and the energetic position of the occupie d LPDOS of the valence band measured by nonresonantly excited SXE spectrosc opy is nearly identical for the three polytypes, reflecting the local ident ity of the crystalline structures. The variation of the band gap from 2.2 e V for 3C-SiC to 3.0 eV for 6H-SiC, and 3.3 eV for 4H-SiC is caused by chang es of the conduction band alone as reflected by the unoccupied LPDOS measur ed by SXA. Additionally, by resonantly excited SXE information on the band dispersion and the local symmetry character of the valence states is obtain ed. [S0163-1829(99)09715-5].