Monte Carlo Simulations on the Thermoelectric Efficiency of a Si Nanowire Modulated by a Constriction

High thermoelectric (TE) efficiency requires good electronic properties and low thermal conductivity. Bulk Si has small ZT mainly due its high thermal conductivity. The thermal conductivity of Si nanowires is significantly lower than in bulk resulting in enhanced TE efficiency. We have previously reported on significant additional reduction of the thermal conductivity of Si nanowires modulated by constrictions based on phonon Monte Carlo simulations. Here, we report on the effect of a constriction on the electron transport properties of Si nanowires based on electron Monte Carlo simulations. The thermoelectric efficiency is estimated from the simulated transport properties of electrons and phonons. We have found that the ZT of a relatively thick Si nanowire modulated by a constriction can be significantly higher than the ZT of the corresponding non-modulated nanowire. The dependence of the ZT enhancement on characteristic dimensions of the nanowire and the constriction are discussed. For the considered modulated nanowires, it is predicted ZT enhancement up to one order of magnitude compared to bulk Si at room temperature.