The cross-plane thermoelectric properties of p-Ge/Si{sub 0.5}Ge{sub 0.5} superlattices

Journal Article · Mon Sep 30 00:00:00 EDT 2013 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4824100· OSTI ID:22217947

Ferre Llin, L.; Samarelli, A.; Weaver, J. M. R.; Dobson, P. S.; Paul, D. J. ^[1]; Cecchi, S.; Chrastina, D.; Isella, G. ^[2]; Etzelstorfer, T.; Stangl, J. ^[3]; Müller Gubler, E. ^[4]

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1. School of Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G12 8LT (United Kingdom)
2. L-NESS, Politecnico di Milano, Via Anzani 42, 22100 Como (Italy)
3. Institute of Semiconductor and Solid State Physics, Johannes Kepler Universität, Linz (Austria)
4. Electron Microscopy ETH Zurich, ETH Zurich, Wolfgang-Pauli-Str. 16, CH-8093 Zurich (Switzerland)

The electrical conductivity, Seebeck coefficients, and thermal conductivities of a range of p-type Ge/Si{sub 0.5}Ge{sub 0.5} superlattices designed for thermoelectric generation and grown by low energy plasma enhanced chemical vapor deposition have been measured using a range of microfabricated test structures. For samples with barriers around 0.5 nm in thickness, the measured Seebeck coefficients were comparable to bulk p-SiGe at similar doping levels suggesting the holes see the material as a random bulk alloy rather than a superlattice. The Seebeck coefficients for Ge quantum wells of 2.85 ± 0.85 nm increased up to 533 ± 25 μV/K as the doping was reduced. The thermal conductivities are between 4.5 to 6.0 Wm{sup −1}K{sup −1} which are lower than comparably doped bulk Si{sub 0.3}Ge{sub 0.7} but higher than undoped Si/Ge superlattices. The highest measured figure of merit ZT was 0.080 ± 0.011 obtained for the widest quantum well studied. Analysis suggests that interface roughness is presently limiting the performance and a reduction in the strain between the quantum wells and barriers has the potential to improve the thermoelectric performance.

• OSTI ID: 22217947
• Journal Information: Applied Physics Letters, Vol. 103, Issue 14; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHEMICAL VAPOR DEPOSITION
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
GERMANIUM
GERMANIUM ALLOYS
GERMANIUM SILICIDES
HOLES
INTERFACES
PERFORMANCE
PLASMA
QUANTUM WELLS
REDUCTION
ROUGHNESS
SEEBECK EFFECT
SEMICONDUCTOR MATERIALS
SILICON ALLOYS
SUPERLATTICES
THERMAL CONDUCTIVITY
THERMOELECTRIC PROPERTIES
THICKNESS