Metal/Semiconductor Nanocomposites for Direct Thermal to Electric Energy Conversion

Thermoelectric effects can be used for direct conversion of heat into electricity using a solid-state device. We describe novel metal/semiconductor nanostructured materials where the heat and charge transport are modified at the atomic level. Hot electron filtering using heterostructure barriers is used to break the trade off between high Seebeck coefficient and high electrical conductivity. Embedded ErAs nanoparticles are used to reduce the lattice thermal conductivity without significant effect on electrical conductivity. The thermal conductivity, electrical conductivity, and Seebeck coefficient of ErAs:InGaAlAs alloys are characterized. The measured ZT is ∼1 at high temperatures 650 K. Integrated circuit fabrication techniques are used to transfer the n- and p-type thin films onto AlN plates and power generation modules are made with hundreds of thin film elements. An output power density >1W/cm2 is demonstrated at an external temperature difference of 120K across the module. Finally, the prospect of other metal semiconductor multilayer structures based on TiN/GaN for high temperature operation will be briefly reviewed.