Refined analysis of the transport properties of Co1−xNixSb3 according to a model including a deep donor level and the second lowest valleys of the conduction band

Experimental data on the transport properties of Co1−xNixSb3 reported by Dyck et al. (2002) have been analyzed, especially focusing on their data above 100 K which had not been analyzed in their original study. In order to explain the data above 100 K, a deep donor level and the second lowest valleys of the conduction band have been included in the analysis model in addition to a shallow donor level and the lowest Γ valley of the conduction band. Not only the effective mass and the deformation potential for the Γ valley of the conduction band but also those of the second lowest valleys have been deduced from simultaneous fits of the Hall coefficient and mobility. The concentrations and the ionization energies of both the shallow and the deep donor level have also been deduced as a function of the Ni content x. The results show that doped Ni atoms are not directly related to the shallow donor impurity band but are directly related to the deep donor level. It is also shown that the large Seebeck coefficient of Co1−xNixSb3 at room temperature originates almost from carriers in the second lowest valleys.