Modeling of Enhanced Thermoelectric Processes Based on Asymmetrically-Graded Superlattices
Final rept. 25 Aug 2003-15 May 2004
NORTH CAROLINA STATE UNIV AT RALEIGH RESEARCH ADMINISTRATION AND SPONSORED PROGRAMS SERVICES
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In this study, we explore the influence of spatially graded energy bands on the thermoelectric properties of thin film semiconductors. In the analysis, we utilize the semi-classical Boltzmann equation in the relaxation approximation. The thermoelectric variables are calculated in terms of spatially varying, band engineered conduction and valence band edges, and a spatially dependent electron-phonon relaxation time based on longitudinal acoustic dispersion use is made of the spherical band approximation and a spatially dependent effective mass for conduction and valence hand carriers to obtain explicit parametric results for the Seebeck coefficient and the figure of merit for a model slab of material of finite length. The Seebeck coefficient is determined and is shown to be enhanced by the addition of a term which depends analytically upon a spatial average of the relative band engineered energy hand edge divided by k Tx, where Tx is the spatially dependent temperature across the sample. The figure of merit, Z T, is also estimated in terms of band engineered variables and discussed in the light of a variational principle which allows for the optimization of Z T. Suggestions for more detailed and rigorous analysis of thermoelectric transport and optimization of Z T are discussed.
- Electricity and Magnetism
- Solid State Physics