First-principles study of the optical properties of SiC

We examine the optical properties of SiC in the 3C, 2H, 4H, and 6H structures through first-principles pseudopotential calculations. The dielectric response function in the optical limit exhibits anisotropic behaviour for the hexagonal polytypes, which arises from hexagonal crystal fields. In the 6H structure, we find that the density of states near the conduction band edge is rapidly increasing and the optical response is significantly enhanced in the ultraviolet energy region. Such peculiar behaviour in the density of states and the dielectric response lead us to understand that 6H SiC is a more promising material for optical devices, compared with other polytypes.