Electrical Properties of Heavily Al-Doped 4H-SiC

Abstract

We investigate the temperature-dependent resistivity (ρ(T)) and Hall coefficient (RH(T)) of heavily Al-doped 4H-SiC and discuss the underlying conduction mechanisms. The sign of RH(T) changes from positive to negative in nearest-neighbor hopping (NNH) and variable-range hopping (VRH) conduction, whereas it is positive in band conduction because Al-doped 4H-SiC is a p-type semiconductor. We propose a general physical model to explain why RH(T) in hopping conduction becomes negative at low temperatures, which is applicable to both NNH and VRH conduction. Moreover, we elucidate why the activation energy for negative RH(T) becomes similar to that of ρ(T) in NNH conduction.