Ge/SiGe-based thermoelectric generator

TK Electrical engineering. Electronics Nuclear engineering

Odia, Ameze ; Paul, Douglas

University:University of Glasgow

Department:School of Engineering

关键词: Ge/SiGe superlattice, thermoelectric generator,finite element (FE) modelling, unicoupled TEG.;   

Others  :  http://theses.gla.ac.uk/8174/7/2017OdiaPhD.pdf

来源: University of Glasgow

【 摘 要 】

This thesis summarizes the milestones achieved in building a thermoelectricgenerator (TEG) device using a novel p- and n- type 2-D thermoelectric materialcalled Ge/SiGe superlattice; which was grown by low energy plasma- enhancedchemical vapour deposition (LEPECVD). It begins by describing in a nutshell theadvances made in the area of thermoelectrics since its inception in 1821, to thepresent application of nanotechnology to develop state-of-the-artthermoelectric materials of which the aforementioned material is one. Next,characterisation of the Ge/SiGe superlattice using a combination of experimentand Finite Element (FE) modelling is explained and the results obtained arediscussed in comparison with published experimental results. Thereafter,experimental and FE results of the application of the Ge/SiGe superlattice tofabricate a TEG device are presented and discussed. The experimental results onthe fabrication of Ge/SiGe TEG device is the first major success at achievingpractically feasible voltage output of up to 2.16 mV. For ease of comparison withother published work, an effective Seebeck coefficient of 471.9V/K wasestimated. At impedance matched loads of 15  and temperature differencemeasured across the device of 5.6 K, a power density of 0.111 W/cm2 andthermal efficiency factor of 0.0035 Wcm-2 K-2 were also estimated. The resultsthough comparable to a few published works, still required furtherimprovements. The limitations of the TEG that resulted to the lowaforementioned performances were discussed; some of which include therestriction of the TEG to a unicouple, having only one p- and n-leg. Thislimitation is related to the development of the p-type Ge/SiGe material whichwas identified during the course of this research work. Another major limitationis that the improvised design of the unicoupled TEG, makes use of indiumbonding to connect the p- and n- legs electrically in series and thermally inparallel. Indium has a low melting temperature of about 120ºC. Hence increasingthe heat source above this temperature will dislocate the legs. The consequenceof this is that the attainment of a significant temperature difference across theTEG that will eventually result to a high Seebeck voltage, based on the Seebeckeffect principle, is limited.Ways to address these problems were therefore discussed as recommendationsfor future research work.