Anomalous charge carrier transport phenomena in highly aluminum doped SiC

Temperature dependant Hall effect measurements were performed on aluminum doped SiC samples with specific resistivities between 8 ohm cm and 0.1 ohm cm. In all samples indications for impurity conduction at low temperatures were found. In low doped samples, a sharp transition between the impurity conduction transport regime and the hole conduction regime is visible in the temperature dependence of specific resistivity, charge carrier concentration and mobility. In highly doped samples (rho < 0.2 ohm cm), this transition is no longer confined to a small temperature range and much less abrupt. We conclude that the impurity conduction is still present at high temperatures in highly aluminum doped SiC so that at least two competing transport mechanisms are present simultaneously in these samples.