Segmented Power Generator Modules of Bi 2 Te 3 and ErAs: InGaAlAs Embedded with ErAs Nanoparticles
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1044-U10-06
Segmented Power Generator Modules of Bi2Te3 and ErAs:InGaAlAs Embedded with ErAs Nanoparticles Gehong Zeng1, Je-Hyeong Bahk, 1, John E. Bowers1, Hong Lu2, Joshua M. O. Zide2, Arthur C. Gossard2, Rajeev Singh3, Zhixi Bian3, Ali Shakouri3, Suzanne L. Singer4, Woochul Kim4, and Arun Majumdar4 1 Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA, 93106 2 Materials Department, University of California, Santa Barbara, CA, 93106 3 Electrical Engineering Department, University of California, Santa Cruz, CA, 95064 4 Department of Mechanical Engineering, University of California, Berkeley, CA, 94720
ABSTRACT We report the fabrication and characterization of segmented element power generator modules of 254 thermoelectric elements. The element is 1 mm × 1 mm in area, which consists of 300 µm thickness Bi2Te3 and 50 µm thickness ErAs:(InGaAs)1-x(InAlAs)x, so that each segment can work at different temperature ranges. Erbium arsenide metallic nanoparticles are incorporated to create scattering centers for middle and long wavelength phonons, provide charge carriers, and form local Schottky barriers for electron filtering. The thermoelectric properties of ErAs:InGaAlAs were characterized by variable temperature measurements of thermal conductivity, electrical conductivity and Seebeck coefficient from 300 K to 600 K. Generator modules of Bi2Te3 and ErAs:InGaAlAs segmented elements were fabricated and an output power over 5.5 W was measured. The performance of the thermoelectric generator modules can further be improved by improving the thermoelectric properties of the element material, and reducing the electrical and thermal parasitic losses. INTRODUCTION The performance of a thermoelectric generator module depends largely on the material’s thermoelectric properties, which are often summarized with the figure of merit, Z = α2σ/κ, where α is Seebeck coefficient, σ is electrical conductivity and κ is thermal conductivity. Thermoelectric properties can be improved by introducing nanometer scale structure into materials: the power factor (α2σ) can be enhanced because of the quantum confinement effect;[1] thermal conductivity can be reduced due to the increase of phonon interface scattering;[2] and the Seebeck coefficient can be increased through thermionic emission.[3-6] Thermal conductivity reduction using superlattice heterostructures or incorporation of nanoparticles has been demonstrated[7-9], and most of the recent ZT improvements come
mainly from the reduction of thermal conductivity. In our study, ErAs nanoparticles, a rocksalt semimetal nanostructure, were epitaxially incorporated into (InGaAs)1-x(InAlAs)x using molecular beam epitaxy (MBE). The ErAs nanoparticles in the InGaAlAs can provide both charge carriers, and create phonon scattering centers. Experiments show that the ErAs nanoparticles form effective phonon scatting centers for middle and long wavelength phonons, and therefore the thermal conductivity can be reduced. When ErAs nanoparticles are incorporated int
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