Enhanced thermoelectric figure of merit in highly-doped silicon nanowires via a corrugated surface modulation

Abstract

Silicon nanowire has attracted considerable attention in thermoelectric devices because the diameter reduction can reduce thermal conductivity with boundary scattering, improving the figure of merit. Nevertheless, there are some challenges in device fabrication due to the relatively low efficiency and the difficulties in mass production. Here, we suggest the silicon nanowire with a corrugated surface to overcome these drawbacks by using a deep reactive-ion etcher. Corrugated silicon nanowires can significantly increase the figure of merit, which is caused by the further reduction of the thermal conductivity originating from phonon backscattering. Therefore, the phosphorus- and boron-doped silicon nanowires with a diameter of 173 nm and 191 nm show very low thermal conductivities of 6.1 and 4.9 W·m–1·K–1, respectively. Notably, these values stand as the lowest values among silicon nanowires previously reported by dry etching at 300 K. As a result, the figure of merit reaches 0.314 for n-type and 0.268 for p-type at 400 K without the diameter scaling of a nanowire.