We introduce the modulation-doping strategy in bulk SiGe nanostructures to improve the thermoelectric power factor. By separating charge carriers from their parent atoms via embedding heavily doped nanoparticles inside an intrinsic host matrix, the ionized impurity scattering rate could be largely reduced, resulting in enhanced mobility. By band engineering, the carriers can spill over from nanoparticles into the host matrix, resulting in similar carrier concentrations, Fermi levels and consequently Seebeck coefficients as those of the uniform nanocomposites. In addition, nanoparticles with low thermal conductivities can further reduce the overall thermal conductivity of the sample. Combining the enhanced electrical conductivity, the reduced thermal conductivity and the unaffected Seebeck coefficient, we were able to enhance the thermoelectric properties of Si-rich Si95Ge5. And therefore were able to fabricate a low-cost sample with a competitive performance as those of the state of the art Si80Ge20.

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