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Transient Harman Measurement of the Cross-plane ZT of InGaAs/InGaAlAs Superlattices with Embedded ErAs Nanoparticles

Published online by Cambridge University Press:  01 February 2011

Rajeev Singh
Affiliation:
rsingh@soe.ucsc.edu, University of California, Santa Cruz, Electrical Engineering, 1156 High St., Santa Cruz, CA, 95064, United States, (831) 459-1292
Zhixi Bian
Affiliation:
zxbian@soe.ucsc.edu, University of California, Santa Cruz, Electrical Engineering Department, United States
Gehong Zeng
Affiliation:
gehong@ece.ucsb.edu, University of California, Santa Barbara, Department of Electrical and Computer Engineering, United States
Joshua Zide
Affiliation:
jmz@engineering.ucsb.edu, University of California, Santa Barbara, Department of Electrical and Computer Engineering
James Christofferson
Affiliation:
jchrist@soe.ucsc.edu, University of California, Santa Cruz, Electrical Engineering Department, United States
Hsu-Feng Chou
Affiliation:
hubert@ece.ucsb.edu, University of California, Santa Barbara, Department of Electrical and Computer Engineering, United States
Art Gossard
Affiliation:
gossard@engineering.ucsb.edu, University of California, Santa Barbara, Department of Electrical and Computer Engineering, United States
John Bowers
Affiliation:
bowers@ece.ucsb.edu, University of California, Santa Barbara, Department of Electrical and Computer Engineering, United States
Ali Shakouri
Affiliation:
ali@soe.ucsc.edu, University of California, Santa Cruz, Electrical Engineering Department, United States
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Abstract

The transient Harman technique is used to characterize the cross-plane ZT of InGaAs/InGaAlAs superlattice structures with embedded ErAs nanoparticles in the well layers. ErAs nanoparticles have proven to substantially reduce the thermal conductivity while slightly increasing the electrical conductivity of bulk InGaAs. The InGaAs/InGaAlAs superlattice structure was designed to have a barrier height of approximately 200meV. Although ErAs nanoparticles provide free carriers inside the semiconductor matrix, additional doping with Si increased the Fermi energy to just below the barrier height. The bipolar transient Harman technique was used to measure device ZT of samples with different superlattice thicknesses in order to extract the intrinsic cross-plane ZT of the superlattice by eliminating the effects of device Joule heating and parasitics. High-speed packaging is used to reduce signal ringing due to electrical impedance mismatch and achieve a short time resolution of roughly 100ns in transient Seebeck voltage measurement. The measured intrinsic cross-plane ZT of the superlattice structure is 0.13 at room temperature. This value agrees with calculations based on the Boltzmann transport equation and direct measurements of specific film properties. Theoretical calculations predict cross-plane ZT of the superlattice to be greater than 1 at temperatures greater than 700K.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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References

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