Experimental and theoretical analysis of the hall-mobility in n-type bulk 6H-and 4H-SiC

The electrical properties of nitrogen doped n-type 6H- and 4H-SiC bulk crystals grown by the Lely- or modified Lely-method have been characterized by Hall-measurements. The doping densities were determined by a fit of the neutrality equation to the experimental data, accounting for in-equivalent lattice sites and the temperature dependence of the effective density-of- states-mass extracted from recent results of ab-initio-calculations of the 6H- and 4H-SiC bandstructure [1]. The theoretical analysis of the Hall-mobility is based on an extended form of the Rode-Nag iteration algorithm [2]. The calculation scheme considers all relevant elastic and inelastic scattering mechanisms, the anisotropy of the crystal modifications and the possible effect of spatial inhomogeneities in the distribution of donors, accepters or in the related electron system. Within these concepts it is possible to achieve a quantitative agreement between theoretical and experimental mobility data in 4H- and 6H-SiC over the whole temperature range of band conduction. New values for the acoustic deformation potentials E-ac [15.0+/-0.5 eV (6H), 14.8+/-0.5 eV (4H)] and the coupling constants for intervalley phonon scattering D-int [2.3+/-0.1 x 10(9) eV/cm (6H), 2.6+/-0.1 x 10(9) eV/cm (4H)] are given.