Tailoring Charge Carrier Mobility in Percolating Solid Solutions for Next Generation Semiconductors

Abstract

The semiconductor \((Bi_{1-x}Sb_x)_2Te_3\) solid solutions obtained by cation substitution Bi\(\to\)Sb are well-known as promising materials used in thermoelectric (TE) cooling devices. The polycrystalline samples of these solid solutions in the range of compositions x = 0 - 0.07 were synthesized, and the dependences of microhardness, electrical conductivity, the Hall coefficient, the Seebeck coefficient, and mobility of charge carriers on x were obtained at room temperature. It was established that in the concentration dependences of all studied properties, the anomalies are observed at the small content of introduced components which indicated the presence of a phase transition. It was assumed that this phase transition has a percolation nature and indicates that at a certain concentration of the impurity component (Sb), a continuous chain of interacting impurity atoms that penetrates the crystal (an infinite cluster) is formed, and then the interaction becomes collective. The experimental results are analyzed in terms of percolation theory considering alloy scattering and spatial correlations of impurity centers. The obtained data are another confirmation of our earlier stated assumption about the universal character of critical phenomena of percolation type accompanying the transition from impurity discontinuum to impurity continuum. The existence of these critical phenomena should be taken into account when developing and interpreting the properties of materials.