Switchable p–n–p conduction and thermoelectric properties of selenium-doped tellurium crystal

Switchable conductivity in elementary semiconducting materials has a high potential for the design of diodes, transistors and energy conversion technologies. However, the ability to utilize their physical properties is dependent on doping within the carrier density transition temperature. Single-crystal tellurium has a high Seebeck coefficient and intrinsic p–n–p conduction at room temperature and therefore, is not suitable for thermoelectric applications. We demonstrate that the addition of isovalent Se lowers the Fermi level to achieve a stable p-type conductivity with a high band degeneracy near the valence band. We observed shifts in the n–p transition temperature below the intrinsic conductivity at 470 K based on changes in stoichiometry and carrier concentration above 10¹⁷ cm⁻³. In addition, the high thermal conductivity is significantly reduced with the increase in Se alloying due to the mass and strain fluctuations. This results in a moderately high zT of 0.4 at 673 K.