Optimisation of the Thermoelectric Figure of Merit of Modified Silicon Germanium Alloys
Interim rept. no. 2
UNIVERSITY OF WALES INST OF SCIENCE AND TECHNOLOGY CARDIFF DEPT OF PHYSICS ELECTRONICS/ELECTRICAL ENGRG
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In this report a working theoretical model for the power factor alpha squared sigma of silicon germanium alloys is presented and the dependence of this parameter on carrier concentration and number of valleys explored. Although silicon-germanium alloys cannot be described as narrow band gap semiconductors, the high level of doping employed in thermoelectric applications necessitates the inclusion in the theoretical model of deviations from the usually assumed parabolic bands. The dependence of the Seebeck coefficient alpha, electrical conductivity sigma and the power factor alpha squared sigma on carrier concentration and number of valleys N sub v are presented. Two main conclusions can be drawn from the reported results. A large number of equi-energetic valleys give rise to a higher power factor at room temperature, when intervalley scattering can be considered negligibly small. Higher doping levels are required in order to take advantage of the large number of valleys. Keywords Semiconductors.
- Metallurgy and Metallography
- Solid State Physics