  We have studied the electronic band properties of 2H-SiC and 4H-SiC silicon
carbide polytypes. The structures of the electronic bands and density of state
(DOS) using ab initio Density Functional Theory (DFT) were calculated for the
first Brillouin zone both in the generalized gradient approximation and taking
into account quasiparticle effects according to the GW scheme. The calculated
bandgaps obtained using the GW approximation ${E_{\rm{g 2H-SiC}} = 3.17}$ eV
and ${E_{\rm{g 4H-SiC}} = 3.26}$ eV agree well with experimental values. The
shape and values of total DOS are within agreement with calculations performed
by other authors. The calculated total energy values for 2H-SiC and 4H-SiC were
close, but they satisfy the condition ${E_{\rm{2H}} > E_{\rm{4H}}}$, which
implies that the 4H-SiC structure is more stable than 2H-SiC. Our calculations
of the band structure and DOS of 2H-SiC and 4H-SiC by the DFT method showed
that the application of the GW approximation is an optimum approach to the
study of the electronic structure of 2H-SiC and 4H-SiC polytypes.
