Thermoelectric properties of electrically gated bismuth telluride nanowires

We theoretically studied the effect of the perpendicular electric field on the thermoelectric prop- erties of the intrinsic, n type and p type bismuth telluride nanowires with the growth direction (110). The electronic structure and the wave functions were calculated by solving self-consistently the system of the Schrodinger and Poisson equations using the spectral method. The Poisson equation was solved in terms of the Newton - Raphson method within the predictor-corrector approach. The electron - electron exchange - correlation interactions were taken into account in our analysis. In the temperature range from 77 to 500 K, the dependences of the Seebeck coefficient, thermal conductiv- ity, electron (hole) concentration, and thermoelectric figure of merit on the nanowire thickness, gate voltage, and excess hole (electron) concentration were investigated in the constant relaxation-time approximation. The results of our calculations indicate that the external perpendicular electric field can increase the Seebeck coefficient of the bismuth telluride nanowires with thicknesses of 7 - 15 nm by nearly a factor of 2 and enhance ZT by an order of magnitude. At room temperature, ZT can reach a value as high as 3.4 under the action of the external perpendicular electric field for realistic widths of the nanowires. The obtain results may open up a completely new way for a drastic enhancement of the thermoelectric figure of merit in a wide temperature range.