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Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first principles calculations
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Date
2019-12-02
Authors
Murphy-Armando, Felipe
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AIP Publishing
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Abstract
We use first-principles electronic structure methods to calculate the electronic thermoelectric properties (i.e., due to electronic transport only) of single-crystalline bulk n-type silicon-germanium alloys vs Ge composition, temperature, doping concentration, and strain. We find excellent agreement to available experiments for the resistivity, mobility, and Seebeck coefficient. These results are combined with the experimental lattice thermal conductivity to calculate the thermoelectric figure of merit ZT, finding very good agreement with experiments. We predict that 3% tensile hydrostatic strain enhances the n-type ZT by 50% at carrier concentrations of n=1020cm−3 and a temperature of T=1200K. These enhancements occur at different alloy compositions due to different effects: at 50% Ge composition, the enhancements are achieved by a strain induced decrease in the Lorenz number, while the power factor remains unchanged. These characteristics are important for highly doped and high temperature materials, in which up to 50% of the heat is carried by electrons. At 70% Ge, the increase in ZT is due to a large increase in the electrical conductivity produced by populating the high mobility Γ conduction band valley, lowered in energy by strain.
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Keywords
Electronic thermoelectric properties , Single-crystalline bulk n-type silicon-germanium alloys , Ge composition , Temperature , Doping concentration , Strain , Resistivity , Mobility , Seebeck coefficient
Citation
Murphy-Armando, F. (2019) ‘Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first principles calculations’, Journal of Applied Physics, 126, 215103 (9pp). doi: 10.1063/1.5117345
Copyright
© 2019, the Author. Published under license by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared as: Murphy-Armando, F. (2019) ‘Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first principles calculations’, Journal of Applied Physics, 126, 215103 (9pp), doi: 10.1063/1.5117345, and may be found at https://doi.org/10.1063/1.5117345