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

Abstract

The electronic structure of SiC polytypes is investigated with soft x-ray absorption (SXA) and emission (SXE) spectroscopy studying the local C p and Si $(s+d)$ partial density of states (LPDOS) of n-doped cubic 3C-SiC and hexagonal 4H- and 6H-SiC. The shape and the energetic position of the occupied LPDOS of the valence band measured by nonresonantly excited SXE spectroscopy is nearly identical for the three polytypes, reflecting the local identity of the crystalline structures. The variation of the band gap from $2.2$ eV for 3C-SiC to $3.0$ eV for 6H-SiC, and $3.3$ eV for 4H-SiC is caused by changes of the conduction band alone as reflected by the unoccupied LPDOS measured by SXA. Additionally, by resonantly excited SXE information on the band dispersion and the local symmetry character of the valence states is obtained.