Investigations on Silicon Carbide

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Abstract
Measurements of Hall effect and resistivity up to 1300°K on p‐type hexagonal SiC showed an acceptor level for aluminium of 0.27 ev at zero donor concentration and a not yet identified acceptor level of 0.39 ev. The spin multiplicity of this unknown center appears to be four times smaller than that of the aluminium center, so that we may conclude that this unknown center in non‐ionized state has paired electrons. Taking a temperature dependence of the level depths proportional to that of the bandgap, the density‐of‐states effective mass of the holes amounts to 0.59 m0. The Hall mobility shows at high temperatures the same temperature dependence as that ascribed to scattering of holes by optical phonons. Assuming that optical phonons really come into effect, the behavior of the Hall mobility in the temperature range from 1300° to 300°K can be explained taking also into account the effect of scattering by acoustical phonons and charged impurities. By a study of I–V characteristics of grown junctions in αSiC and also by applying Roosbroeck‐Shockley's theory to the spectral distribution of the p‐n luminescence under forward bias, inhomogeneities were found over the junction area. By means of pyrolysis of gaseous compounds of Si and C pure crystals (4×2×2 mm3) of ``cubic'' βSiC were obtained. With the aid of polarized light the existence of a skeleton of a hexagonal twinning system was found in these crystals, the cubic SiC filling up the pores of this skeleton structure.

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