Enhancement of the Thermoelectricity in Half-Heusler TaRuAs by Substitutional Doping

The electronic structure and thermoelectric response of the half-Heusler compound TaRuAs are studied based on density functional theory, deformation potential theory, and Boltzmann transport theory. The effects of doping are elucidated adopting both the rigid band approximation and supercells that explicitly include the dopant atoms. Our results reveal that TaRuAs has a bandgap of 0.3 eV. The optimal doping concentrations to achieve the highest power factor at 900 K are found to be 2 × 10²¹ and 4 × 10²¹ cm⁻³ for hole and electron doping, respectively. Doping at both the Ru and As sites turns out to be an effective method to enhance the thermoelectric figure of merit, with the highest values achieved by TaRu_7/8Tc_1/8As (0.4) and TaRuAs_7/8Ge_1/8 (0.5), respectively.