High-frequency (95GHz) pulsed electron paramagnetic resonance and electron nuclear double resonance measurements were made of the N donor in 4H-SiC (k-site) and 6H-SiC (h, k1, k2 sites). From the isotropic and anisotropic hyperfine interaction of the unpaired electron spin of the donor with the 13C (35% 13C-enriched samples were used) and 29Si nuclei, the distribution of the electronic wave function of the N donor was determined. It was found that this wave function was quite different in the 2 polytypes because the spin-density distribution over the 13C and 29Si nuclei differs between the 4H and 6H polytypes. A similar conclusion was derived from the electron paramagnetic resonance line broadening of the N donor in 13C-enriched 4H- and 6H-SiC compared with non-enriched crystals. The main part of the spin density in 4H-SiC was located on the Si sub-lattice and the wave function contains a relatively large portion of Si p character. A tentative assignment was proposed for 5 electron nuclear double resonance lines. For the three sites in 6H-SiC, the main part of the spin density was located on the C sub-lattice and the wave function was built mostly of s-like C atomic orbitals. Comparing the 3 sites in 6H-SiC, the h-site wave function has the largest delocalization and was most isotropic. The k2 site wave function was most localized and less isotropic. The largest part of the

spin density was located far into the crystal. The difference in behavior of the wave function in 4H and 6H polytypes seems to find its origin in the difference in their conduction-band structure. The results indicated that the conduction-band minima in 4H-SiC (bottom of the conduction bands) were mainly Si-like, whereas in 6H-SiC the conduction-band minima were mostly C-like.

Electronic Structure of the N Donor Center in 4H-SiC and 6H-SiC. A.V.Duijn-Arnold, R.Zondervan, J.Schmidt, P.G.Baranov, E.N.Mokhov: Physical Review B, 2001, 64[8], 085206 (17pp)