Semiconductor Thermal and Electrical Properties Decoupled by Localized Phonon Resonances
[5];
- Physical Measurement Laboratory National Institute of Standards and Technology (NIST) Boulder CO 80302 USA
- School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China
- Ann and H.J. Smead Department of Aerospace Engineering Sciences University of Colorado Boulder Boulder CO 80303 USA
- Department of Physics University of Colorado Boulder Boulder CO 80302 USA
- Ann and H.J. Smead Department of Aerospace Engineering Sciences University of Colorado Boulder Boulder CO 80303 USA, Department of Physics University of Colorado Boulder Boulder CO 80302 USA
Abstract Thermoelectric materials convert heat into electricity through thermally driven charge transport in solids or vice versa for cooling. To compete with conventional energy‐conversion technologies, a thermoelectric material must possess the properties of both an electrical conductor and a thermal insulator. However, these properties are normally mutually exclusive because of the interconnection between scattering mechanisms for charge carriers and phonons. Recent theoretical investigations on sub‐device scales have revealed that nanopillars attached to a membrane exhibit a multitude of local phonon resonances, spanning the full spectrum, that couple with the heat‐carrying phonons in the membrane and cause a reduction in the in‐plane thermal conductivity, with no expected change in the electrical properties because the nanopillars are outside the pathway of voltage generation and charge transport. Here this effect is demonstrated experimentally for the first time by investigating device‐scale suspended silicon membranes with GaN nanopillars grown on the surface. The nanopillars cause up to 21% reduction in the thermal conductivity while the power factor remains unaffected, thus demonstrating an unprecedented decoupling in the semiconductor's thermoelectric properties. The measured thermal conductivity behavior for coalesced nanopillars and corresponding lattice‐dynamics calculations provide evidence that the reductions are mechanistically tied to the phonon resonances. This finding paves the way for high‐efficiency solid‐state energy recovery and cooling.
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- NONE; AR0001056
- OSTI ID:
- 1983371
- Journal Information:
- Advanced Materials, Journal Name: Advanced Materials Journal Issue: 26 Vol. 35; ISSN 0935-9648
- Publisher:
- Wiley Blackwell (John Wiley & Sons)Copyright Statement
- Country of Publication:
- Germany
- Language:
- English
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