Thermoelectric properties of gated Si nanowires

The thermoelectric (TE) performance of materials is determined by the figure of merit ZT=σS/κ, where σ denotes the electrical conductivity, S the Seebeck coefficient and κ the thermal conductivity. Large improvements in ZT have recently been reported in nanoscale materials due to drastic reduction in κ. Despite this improvement, however, ZT still remains too low for allowing large scale TE deployment, mainly because the power factor (σS) has not been improved so far. A possible way to improve σS is the use of gating rather than doping to achieve the required high charge densities [1]. This removes the strongest scattering mechanism that hinders carrier transport and yields higher conductivity. In this work, we compute the TE power factor in gated Si nanowires (NWs) and compare it to the power factor of doped NWs. We show that although gated structures suffer from reduced Seebeck coefficient, the power factor can be improved by ~5x.