  Semiconductor nanostructures hold great promise for high-efficiency waste
heat recovery exploiting thermoelectric energy conversion, a technological
breakthrough that could significantly contribute to providing environmentally
friendly energy sources as well as in enabling the realization of self-powered
biomedical and wearable devices. A crucial requirement in this field is the
reduction of the thermal conductivity of the thermoelectric material without
detrimentally affecting its electrical transport properties. In this work we
demonstrate a drastic reduction of thermal conductivity in III-V semiconductor
nanowires due to the presence of intentionally realized periodic crystal
lattice twin planes. The electrical and thermal transport of these
nanostructures, known as twinning superlattice nanowires, have been probed and
compared with their twin-free counterparts, showing a one order of magnitude
decrease of thermal conductivity while maintaining unaltered electrical
transport properties, thus yielding a factor ten enhancement of the
thermoelectric figure of merit, ZT. Our study reports for the first time the
experimental measurement of electrical and thermal properties in twinning
superlattice nanowires, which emerge as a novel class of nanomaterials for high
efficiency thermoelectric energy harvesting.
