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Title: Thermal conductivity of GaAs/Ge nanostructures

Superlattices are of great interest as platform materials for thermoelectric technology that are capable of directly converting low-grade heat energy into useful electrical power. In this paper, the thermal conductivities of GaAs/Ge superlattice nanostructures were investigated systematically in relation to their morphologies and interfaces. Thermal conductivities were measured using ultrafast time-domain thermoreflectance and were found to decrease with increasing interface densities, consistent with past understanding of microscopic phonon transport in the particle regime. The lowest thermal conductivities were observed in (GaAs) 0.77(Ge 2) 0.23 alloys, and transmission electron microscopy study reveals phase separation in the alloys. These alloys can be interpreted as fine nanostructures, with length scales comparable to the periods of very thin superlattices. Electrical transport measurements along the film plane direction showed no significant reduction in electrical properties attributable to the interfaces between GaAs and Ge. Finally, our experimental findings help gain fundamental insight into nanoscale thermal transport in superlattices and are also useful for future improvement of thermoelectric performance using nanostructures.
Authors:
 [1] ; ORCiD logo [2] ;  [2] ; ORCiD logo [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Materials Science and Engineering
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Mechanical Engineering
Publication Date:
Grant/Contract Number:
SC0001299; FG02-09ER46577; DMR-14-19807
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 22; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Energy Frontier Research Centers (EFRC) (United States). Solid-State Solar-Thermal Energy Conversion Center (S3TEC)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); National Research Foundation (NRF) (Singapore)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; germanium; electrical properties; phonons; elemental semiconductors; III-V semiconductors; thermal models; superlattices; thermoelectric energy conversion; nanostructures; thermal conductivity
OSTI Identifier:
1466226
Alternate Identifier(s):
OSTI ID: 1366562

Jia, Roger, Zeng, Lingping, Chen, Gang, and Fitzgerald, Eugene A. Thermal conductivity of GaAs/Ge nanostructures. United States: N. p., Web. doi:10.1063/1.4984957.
Jia, Roger, Zeng, Lingping, Chen, Gang, & Fitzgerald, Eugene A. Thermal conductivity of GaAs/Ge nanostructures. United States. doi:10.1063/1.4984957.
Jia, Roger, Zeng, Lingping, Chen, Gang, and Fitzgerald, Eugene A. 2017. "Thermal conductivity of GaAs/Ge nanostructures". United States. doi:10.1063/1.4984957. https://www.osti.gov/servlets/purl/1466226.
@article{osti_1466226,
title = {Thermal conductivity of GaAs/Ge nanostructures},
author = {Jia, Roger and Zeng, Lingping and Chen, Gang and Fitzgerald, Eugene A.},
abstractNote = {Superlattices are of great interest as platform materials for thermoelectric technology that are capable of directly converting low-grade heat energy into useful electrical power. In this paper, the thermal conductivities of GaAs/Ge superlattice nanostructures were investigated systematically in relation to their morphologies and interfaces. Thermal conductivities were measured using ultrafast time-domain thermoreflectance and were found to decrease with increasing interface densities, consistent with past understanding of microscopic phonon transport in the particle regime. The lowest thermal conductivities were observed in (GaAs)0.77(Ge2)0.23 alloys, and transmission electron microscopy study reveals phase separation in the alloys. These alloys can be interpreted as fine nanostructures, with length scales comparable to the periods of very thin superlattices. Electrical transport measurements along the film plane direction showed no significant reduction in electrical properties attributable to the interfaces between GaAs and Ge. Finally, our experimental findings help gain fundamental insight into nanoscale thermal transport in superlattices and are also useful for future improvement of thermoelectric performance using nanostructures.},
doi = {10.1063/1.4984957},
journal = {Applied Physics Letters},
number = 22,
volume = 110,
place = {United States},
year = {2017},
month = {6}
}