Large thermoelectric figure of merit in Si1-x Gex nanowires

Abstract

By using first-principles electronic structure calculation and Boltzmann transport equation, we investigate composition effects on the thermoelectric properties of silicon-germanium (Si1-x Gex) nanowires (NWs). The power factor and figure of merit in n-type Si1-x Ge x wires are much larger than those in their p-type counterparts with the same Ge content and doping concentration. Moreover, the maximal obtainable figure of merit can be increased by a factor of 4.3 in n-type Si0.5 Ge0.5 NWs, compared with the corresponding values in pure silicon nanowires (SiNWs). Given the fact that the measured ZT of n-type SiNW is 0.6∼1.0, we expect Z T value of n-type Si1-x Gex NWs to be 2.5∼4.0. © 2010 American Institute of Physics.